Only if synonym

conjunction

noun

"Iff" redirects here. For other uses, see IFF (disambiguation).

"↔" redirects here. It is not to be confused with Bidirectional traffic.

"⟺" redirects here. For other uses, see Arrow (symbol).

Logical connective

In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff"^[1]) is a biconditionallogical connective between statements, where either both statements are true or both are false.

The connective is biconditional (a statement of material equivalence),^[2] and can be likened to the standard material conditional ("only if", equal to "if then") combined with its reverse ("if"); hence the name. The result is that the truth of either one of the connected statements requires the truth of the other (i.e. either both statements are true, or both are false), though it is controversial whether the connective thus defined is properly rendered by the English "if and only if"—with its pre-existing meaning. For example, P if and only if Q means that P is true whenever Q is true, and the only case in which P is true is if Q is also true, whereas in the case of P if Q, there could be other scenarios where P is true and Q is false.

In writing, phrases commonly used as alternatives to P "if and only if" Q include: Q is necessary and sufficient for P, P is equivalent (or materially equivalent) to Q (compare with material implication), P precisely if Q, P precisely (or exactly) when Q, P exactly in case Q, and P just in case Q.^[3] Some authors regard "iff" as unsuitable in formal writing;^[4] others consider it a "borderline case" and tolerate its use.^[5]

In logical formulae, logical symbols, such as ^[6] and ,^[7] are used instead of these phrases; see §&#;Notation below.

Definition[edit]

The truth table of PQ is as follows:^[8][9]

It is equivalent to that produced by the XNOR gate, and opposite to that produced by the XOR gate.^[10]

Usage[edit]

Notation[edit]

The corresponding logical symbols are "↔",^[6] "",^[7] and "≡",^[11] and sometimes "iff". These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas (e.g., in metalogic). In Łukasiewicz's Polish notation, it is the prefix symbol 'E'.^[12]

Another term for this logical connective is exclusive nor.

In TeX, "if and only if" is shown as a long double arrow: via command \iff.^[13]

Proofs[edit]

In most logical systems, one proves a statement of the form "P iff Q" by proving either "if P, then Q" and "if Q, then P", or "if P, then Q" and "if not-P, then not-Q".^[1] Proving these pair of statements sometimes leads to a more natural proof, since there are not obvious conditions in which one would infer a biconditional directly. An alternative is to prove the disjunction "(P and Q) or (not-P and not-Q)", which itself can be inferred directly from either of its disjuncts—that is, because "iff" is truth-functional, "P iff Q" follows if P and Q have been shown to be both true, or both false.

Origin of iff and pronunciation[edit]

Usage of the abbreviation "iff" first appeared in print in John L. Kelley's book General Topology.^[14] Its invention is often credited to Paul Halmos, who wrote "I invented 'iff,' for 'if and only if'—but I could never believe I was really its first inventor."^[15]

It is somewhat unclear how "iff" was meant to be pronounced. In current practice, the single 'word' "iff" is almost always read as the four words "if and only if". However, in the preface of General Topology, Kelley suggests that it should be read differently: "In some cases where mathematical content requires 'if and only if' and euphony demands something less I use Halmos' 'iff'". The authors of one discrete mathematics textbook suggest:^[16] "Should you need to pronounce iff, really hang on to the 'ff' so that people hear the difference from 'if'", implying that "iff" could be pronounced as [ɪfː].

Usage in definitions[edit]

Technically, definitions are always "if and only if" statements; some texts — such as Kelley's General Topology — follow the strict demands of logic, and use "if and only if" or iff in definitions of new terms.^[17] However, this logically correct usage of "if and only if" is relatively uncommon, as the majority of textbooks, research papers and articles (including English Wikipedia articles) follow the special convention to interpret "if" as "if and only if", whenever a mathematical definition is involved (as in "a topological space is compact if every open cover has a finite subcover").^[18]

Distinction from "if" and "only if"[edit]

• "Madison will eat the fruit if it is an apple." (equivalent to "Only if Madison will eat the fruit, can it be an apple" or "Madison will eat the fruit ← the fruit is an apple")

  This states that Madison will eat fruits that are apples. It does not, however, exclude the possibility that Madison might also eat bananas or other types of fruit. All that is known for certain is that she will eat any and all apples that she happens upon. That the fruit is an apple is a sufficient condition for Madison to eat the fruit.

• "Madison will eat the fruit only if it is an apple." (equivalent to "If Madison will eat the fruit, then it is an apple" or "Madison will eat the fruit → the fruit is an apple")

  This states that the only fruit Madison will eat is an apple. It does not, however, exclude the possibility that Madison will refuse an apple if it is made available, in contrast with (1), which requires Madison to eat any available apple. In this case, that a given fruit is an apple is a necessary condition for Madison to be eating it. It is not a sufficient condition since Madison might not eat all the apples she is given.

• "Madison will eat the fruit if and only if it is an apple." (equivalent to "Madison will eat the fruit ↔ the fruit is an apple")

  This statement makes it clear that Madison will eat all and only those fruits that are apples. She will not leave any apple uneaten, and she will not eat any other type of fruit. That a given fruit is an apple is both a necessary and a sufficient condition for Madison to eat the fruit.

Sufficiency is the converse of necessity. That is to say, given P→Q (i.e. if P then Q), P would be a sufficient condition for Q, and Q would be a necessary condition for P. Also, given P→Q, it is true that ¬Q→¬P (where ¬ is the negation operator, i.e. "not"). This means that the relationship between P and Q, established by P→Q, can be expressed in the following, all equivalent, ways:

P is sufficient for Q

Q is necessary for P

¬Q is sufficient for ¬P

¬P is necessary for ¬Q

As an example, take the first example above, which states P→Q, where P is "the fruit in question is an apple" and Q is "Madison will eat the fruit in question". The following are four equivalent ways of expressing this very relationship:

If the fruit in question is an apple, then Madison will eat it.

Only if Madison will eat the fruit in question, is it an apple.

If Madison will not eat the fruit in question, then it is not an apple.

Only if the fruit in question is not an apple, will Madison not eat it.

Here, the second example can be restated in the form of ifthen as "If Madison will eat the fruit in question, then it is an apple"; taking this in conjunction with the first example, we find that the third example can be stated as "If the fruit in question is an apple, then Madison will eat it; and if Madison will eat the fruit, then it is an apple".

In terms of Euler diagrams[edit]

• 

  A is a proper subset of B. A number is in A only if it is in B; a number is in B if it is in A.

• 

  C is a subset but not a proper subset of B. A number is in B if and only if it is in C, and a number is in C if and only if it is in B.

Euler diagrams show logical relationships among events, properties, and so forth. "P only if Q", "if P then Q", and "P→Q" all mean that P is a subset, either proper or improper, of Q. "P if Q", "if Q then P", and Q→P all mean that Q is a proper or improper subset of P. "P if and only if Q" and "Q if and only if P" both mean that the sets P and Q are identical to each other.

More general usage[edit]

Iff is used outside the field of logic as well. Wherever logic is applied, especially in mathematical discussions, it has the same meaning as above: it is an abbreviation for if and only if, indicating that one statement is both necessary and sufficient for the other.^[1] This is an example of mathematical jargon (although, as noted above, if is more often used than iff in statements of definition).

The elements of X are all and only the elements of Y means: "For any z in the domain of discourse, z is in X if and only if z is in Y."

See also[edit]

References[edit]

External links[edit]

if

  

1  
    conj  admitting, allowing, assuming, granting, in case, on condition that, on the assumption that, provided, providing, supposing, though, whenever, wherever, whether  

2  
    n  condition, doubt, hesitation, stipulation, uncertainty  

make as if    , though  
act as if or though, affect, feign, feint, give the impression that, make a show of, pretend  

---

if

  
Often pronounced ɪf at the beginning of the sentence.    

1    conj  You use if in conditional sentences to introduce the circumstances in which an event or situation might happen, might be happening, or might have happened.  
She gets very upset if I exclude her from anything, You can go if you want, If you went into town, you'd notice all the pubs have loud jukeboxes, Do you have a knack for coming up with ideas? If so, we would love to hear from you.    

2    conj  You use if in indirect questions where the answer is either `yes' or `no'.   (=whether)  
He asked if I had left with you, and I said no, I wonder if I might have a word with Mr Abbot?    

3    conj  You use if to suggest that something might be slightly different from what you are stating in the main part of the sentence, for example that there might be slightly more or less of a particular quality.  
with neg  
Sometimes, that standard is quite difficult, if not impossible, to achieve, I'm working on my fitness and I will be ready in a couple of weeks, if not sooner    

4    conj  You use if, usually with `can', `could', `may', or `might', at a point in a conversation when you are politely trying to make a point, change the subject, or interrupt another speaker.  
If I could just make another small point about the weightlifters in the Olympics    

5    conj  You use if at or near the beginning of a clause when politely asking someone to do something.,  (politeness)   I wonder if you'd be kind enough to give us some information, please?    

6    conj  You use if to introduce a subordinate clause in which you admit a fact which you regard as less important than the statement in the main clause.  
If there was any disappointment it was probably temporary    

7    phrase  You use if not in front of a word or phrase to indicate that your statement does not apply to that word or phrase, but to something closely related to it that you also mention.  
She understood his meaning, if not his words, and took his advice.    

8    phrase  You use if ever with past tenses when you are introducing a description of a person or thing, to emphasize how appropriate it is.,  (emphasis)   I became a distraught, worried mother, a useless role if ever there was one    

9    phrase  You use if only with past tenses to introduce what you think is a fairly good reason for doing something, although you realize it may not be a very good one.  
She writes me often, if only to scold me because I haven't written to her    

10    phrase  You use if only to express a wish or desire, especially one that cannot be fulfilled.,  (feelings)   If only you had told me that some time ago    

11    phrase  You use as if when you are making a judgment about something that you see or notice. Your belief or impression might be correct, or it might be wrong.  
The whole room looks as if it has been lovingly put together over the years    

12    phrase  You use as if to describe something or someone by comparing them with another thing or person.  
He points two fingers at his head, as if he were holding a gun    

13    phrase  You use as if to emphasize that something is not true.  
SPOKEN, emphasis  Getting my work done! My God! As if it mattered.    

14  You use `if anything' to introduce something which strengthens or changes the meaning of the statement you have just made, but only in a small or unimportant way.  
&#; if anything    phrase  PHR with cl  
Living together didn't harm our friendship. If anything it strengthened it    

15  You use `It's not as if' to introduce a statement which, if it were true, might explain something puzzling, although in fact it is not true.  
&#; it's not as if    phrase  V inflects  
I am surprised by the fuss she's making. It's not as if my personality has changed.    

16  You say `if I were you' to someone when you are giving them advice.  
&#; if I were you    phrase  PHR with cl  
If I were you, Mrs Gretchen, I just wouldn't worry about it    

---

• you catch more flies with honey  exp. The actual say is: "You can catch more flies with honey than with vinegar" This means that it is easier to persuade people if you use polite arguments and flattery than if you are confrontational.
• FOB  n. Free On Board: A legal term meaning that when the seller loads merchandise for transportation, he bears full responsibility for it but if the merchandise is later lost or harmed, the buyer suffers the loss.
• jailbait  n. underaged girl looking mature, that can thus bring somebody to jail if he is caught in a relationship with her
  

  made with Jail and Bait

• locavore  n. a person whose diet consists principally, if not only, of locally grown or produced food
  

  Ex: Having concerns about ecological issues I became a locavore even if I have to make concessions for staples such as coffee, tea, salt or sugar which are difficult to find close to home

• bookjacker  n. someone who re-posts a genuine online listing for a book at an inflated price on another website. If someone buys from the bookjacker, he buys the book from the original seller and provides him with the address of the customer. The bookjacker never sees or handles the book, but collects his margin.
  

  Syn. dropshipper.

• still the mind  exp. to rest the mind, to stop if from overthinking, to relax
• can't be arsed  exp. if you can't be arsed to do something, you can't be bothered to do it (you are too lazy to do it)
  

  colloquial, British, very common

• criminal check  n. verification conducted by police to find out if a person has a criminal record or not.
  

  Usually requested by an individual for new employment, citizenship applications, name changes, etc.

• regression test  n. is a test process that is performed after the software has been changed in order to verify if the changes didn't affect other software parts
• love me, love my dog  exp. expression used for pointing out that, if you love someone, you accept also things and people dear to the person you love
• pride comes before fall  id. def.: if you are too confident about yourself, something bad will happen to show you that you are not as good as you think you are
• live in each other's pocket  exp. if people live in each other's pocket, they spend a lot of time together
• more holes than a Swiss cheese  adj. a phrase to qualify something that has a lot of faults and problems. If an argument or a story has more holes than the distinctive gaps in the said Swiss cheese, it&#;s definitely got a lot of issues.
  

  Ex.: I didn't enjoy his last movie at all; the plot had more holes than a Swiss cheese and the scenario was totally improbable.

• albeit : "Reality is merely an illusion,albeit a very persistent one!"  conj. albeit although, even if, even though, notwithstanding that, tho' (U.S. or poetic) though <You use albeit to introduce a fact or comment which reduces the force or significance of what you have just said. FORMAL adv ADV with cl/group (=although)
  

  Charles's letter was indeed published, albeit in a somewhat abbreviated form.

Alphabetical index

The token filter allows to easily handle synonyms during the analysis process. Synonyms are configured using a configuration file. Here is an example:

The above configures a filter, with a path of (relative to the location). The analyzer is then configured with the filter.

This filter tokenizes synonyms with whatever tokenizer and token filters appear before it in the chain.

Additional settings are:

With the above request the word gets skipped but a mapping is still added. However, if the mapping being added was nothing would get added to the synonym list. This is because the target word for the mapping is itself eliminated because it was a stop word. Similarly, if the mapping was "bar, foo, baz" and was set to no mapping would get added as when the target mapping is the first word. However, if then the mappings added would be equivalent to i.e, all mappings other than the stop word.

and are deprecatededit

The parameter controls the tokenizers that will be used to tokenize the synonym, this parameter is for backwards compatibility for indices that created before The parameter works with parameter only.

Two synonym formats are supported: Solr, WordNet.

Solr synonymsedit

The following is a sample format of the file:

You can also define synonyms for the filter directly in the configuration file (note use of instead of ):

However, it is recommended to define large synonyms set in a file using , because specifying them inline increases cluster size unnecessarily.

WordNet synonymsedit

Synonyms based on WordNet format can be declared using :

Using to define WordNet synonyms in a file is supported as well.

Parsing synonym filesedit

Elasticsearch will use the token filters preceding the synonym filter in a tokenizer chain to parse the entries in a synonym file. So, for example, if a synonym filter is placed after a stemmer, then the stemmer will also be applied to the synonym entries. Because entries in the synonym map cannot have stacked positions, some token filters may cause issues here. Token filters that produce multiple versions of a token may choose which version of the token to emit when parsing synonyms, e.g. will only produce the folded version of the token. Others, e.g. , or will throw an error.

If you need to build analyzers that include both multi-token filters and synonym filters, consider using the multiplexer filter, with the multi-token filters in one branch and the synonym filter in the other.

`` copied!

Purpose

Use the statement to create a synonym, which is an alternative name for a table, view, sequence, procedure, stored function, package, materialized view, Java class schema object, user-defined object type, or another synonym.

Synonyms provide both data independence and location transparency. Synonyms permit applications to function without modification regardless of which user owns the table or view and regardless of which database holds the table or view. However, synonyms are not a substitute for privileges on database objects. Appropriate privileges must be granted to a user before the user can use the synonym.

You can refer to synonyms in the following DML statements: , , , , , , and .

You can refer to synonyms in the following DDL statements: , , , , and .

Prerequisites

To create a private synonym in your own schema, you must have the system privilege.

To create a private synonym in another user's schema, you must have the system privilege.

To create a synonym, you must have the system privilege.

Syntax

create_synonym::=

Semantics

OR REPLACE

Specify to re-create the synonym if it already exists. Use this clause to change the definition of an existing synonym without first dropping it.

Restriction on Replacing a Synonym You cannot use the clause for a type synonym that has any dependent tables or dependent valid user-defined object types.

PUBLIC

Specify to create a public synonym. Public synonyms are accessible to all users. However each user must have appropriate privileges on the underlying object in order to use the synonym.

When resolving references to an object, Oracle Database uses a public synonym only if the object is not prefaced by a schema and is not followed by a database link.

If you omit this clause, then the synonym is private and is accessible only within its schema. A private synonym name must be unique in its schema.

Notes on Public Synonyms The following notes apply to public synonyms:

• If you create a public synonym and it subsequently has dependent tables or dependent valid user-defined object types, then you cannot create another database object of the same name as the synonym in the same schema as the dependent objects.

• Take care not to create a public synonym with the same name as an existing schema. If you do so, then all PL/SQL units that use that name will be invalidated.

schema

Specify the schema to contain the synonym. If you omit , then Oracle Database creates the synonym in your own schema. You cannot specify a schema for the synonym if you have specified .

synonym

Specify the name of the synonym to be created.

FOR Clause

Specify the object for which the synonym is created. The schema object for which you are creating the synonym can be of the following types:

• Table or object table

• View or object view

• Sequence

• Stored procedure, function, or package

• Materialized view

• Java class schema object

• User-defined object type

• Synonym

The schema object need not currently exist and you need not have privileges to access the object.

Restriction on the FOR Clause The schema object cannot be contained in a package.

schema Specify the schema in which the object resides. If you do not qualify object with , then the database assumes that the schema object is in your own schema.

If you are creating a synonym for a procedure or function on a remote database, then you must specify in this statement. Alternatively, you can create a local public synonym on the database where the object resides. However, the database link must then be included in all subsequent calls to the procedure or function.

dblink  You can specify a complete or partial database link to create a synonym for a schema object on a remote database where the object is located. If you specify and omit , then the synonym refers to an object in the schema specified by the database link. Oracle recommends that you specify the schema containing the object in the remote database.

If you omit , then Oracle Database assumes the object is located on the local database.

Restriction on Database Links You cannot specify for a Java class synonym.

Examples

CREATE SYNONYM: Examples To define the synonym for the table in the schema , issue the following statement:

To create a synonym for the table in the schema on the database, you could issue the following statement:

A synonym may have the same name as the underlying object, provided the underlying object is contained in another schema.

Oracle Database Resolution of Synonyms: Example Oracle Database attempts to resolve references to objects at the schema level before resolving them at the synonym level. For example, the schemas and s both contain tables named . In the next example, user creates a synonym named for :

If the user then issues the following statement, then the database returns the count of rows from :

To retrieve the count of rows from , the user must preface with the schema name. (The user must have select permission on as well.)

If the user 's schema does not contain an object named , and if has select permission on , then can access the table in 's schema by using the public synonym :

A synonym is simply a word that means the same as the given word. It comes from the Greek “syn” and “onym,” which mean “together” and “name,” respectively. When speaking or writing, one of the best ways to expand your vocabulary and to avoid using the same words repeatedly is to use a thesaurus to find synonyms (similar meaning words). A thesaurus is a general phrase that describes a type of dictionary that provides a list of words that have the same or similar meaning as the word referenced. For example, if you were to look up the word “beautiful,” you might get a listing of more than thirty words that have similar meanings. There are many forms of a thesaurus from Roget’s Thesaurus, authored by Peter Mark Roget and published in , to online materials available from companies that specialize in educational resources.

Why is it Important to Use Synonyms in your Speech or Writing?

It is important because synonyms can help you enhance the quality of your writing by providing your readers with a crisp and unique outlook of your text. Furthermore, it can also improve both your oral skills and your writing skills, as noted in the following section.

What are the Benefits of Using Synonyms in Writing?

Some of the benefits of using synonyms are that they can:

• Make text much more captivating.
• Help avoid dull text.
• Improve communication between you and others.
• Help provide an image in the mind of the reader.
• Help avoid boring and repetitive text.

Related: Having difficulty with language and grammar in your thesis? Check out these helpful resources now!

For example, instead of using the word “beautiful” several times in your text, you might use synonyms such as “gorgeous,” “stunning,” or “ravishing” to better paint a picture of your description. Using just one word repeatedly will ensure that you will lose the attention of your audience simply out of boredom!

It is quite easy to build your arsenal of synonyms, and the list of tools later in this article will help you get started. As with any efforts to increase your vocabulary, it is helpful to keep a journal or list of new words to which to refer. It is also helpful to use those new synonyms often to keep them in your memory. The more you use new words, the more quickly they will come to mind in your oral or written presentations.

Avoiding Plagiarism using Paraphrasing with Synonyms

Plagiarism is a serious issue for writers and editors and is considered copyright infringement. It is particularly serious for academic researchers because plagiarizing someone else’s work in a research document can diminish or even destroy their professional credibility. Any works that you refer to in your writings that are not your original thoughts or ideas should be correctly cited and referenced. Must you always use direct quotations? Not necessarily, but any part of the original text that you include in your paraphrased text should be in quotation marks.

Paraphrasing allows us to reduce a very lengthy quotation by using fewer words to convey the same message, and it can help avoid the temptation to use too many quotations. This is where synonyms come in handy, but you must be mindful of what words to use.

How to Paraphrase Without Plagiarizing

When paraphrasing, be sure of the following points:

• The words you choose to replace the original idea are true synonyms. For example, the original phrase, “It was a dark day,” could mean more than one thing. It could mean that the weather was gloomy or that the person’s mood was somber and depressed.
• Be sure that you grasp the original idea and use words that will convey the same meaning.

Recommended Tools/Websites for finding Synonyms

Several books and websites can help you build your dictionary of synonyms. One of the most often used publications is Roget’s Thesaurus, which is available in both hardcopy and electronically after downloading from an online source. Below are some of the recommended tools/websites for finding appropriate synonyms:

• The Visual Thesaurus® is an interactive dictionary that allows you to type in a word for which you want a synonym and then creates “word maps” of related words. It also provides definitions.
• Thesaurus.com is another interactive reference tool that not only provides http://www.thesaurus.com/synonyms and other related words, but also categorizes them based on complexity and length, and whether the word is used formally or informally. The site also features a “word of the day” as an aid for building your vocabulary.
• Synonyms.net provides synonyms, antonyms, definitions, and even translation of the word into several other languages.
• Reverso Dictionary not only provides synonyms but also translations of a word in other languages.

Learning to use synonyms effectively can help you better communicate your ideas. Clear and concise text using a variety of synonyms can provide your readers with more interesting reading that will hold their interest. After all, this is ultimately the goal in academic writing so that new topics and research can be clearly presented to anyone interested.