in case that; granting or supposing that; on condition that: Sing if you want to. Stay indoors if it rains. I'll go if you do.
even though: an enthusiastic if small audience.
whether: He asked if I knew Spanish.
(used to introduce an exclamatory phrase): If only Dad could see me now!
when or whenever: If it was raining, we had to play inside.
a supposition; uncertain possibility: The future is full of ifs.
a condition, requirement, or stipulation: There are too many ifs in his agreement.
ifs, ands, or buts, reservations, restrictions, or excuses: I want that job finished today, and no ifs, ands, or buts.

before 900; Middle English, variant of yif, Old English gif, gef; akin to Old Norse ef if, Gothic ibai whether, Old High German iba condition, stipulation

1, 2. If, provided, providing imply a condition on which something depends. If is general. It may be used to indicate suppositions or hypothetical conditions (often involving doubt or uncertainty): If you like, we can go straight home. If I had known, I wouldn't have gone. If may mean even though: If I am wrong, you are not right. It may mean whenever: If I do not understand, I ask questions. Provided always indicates some stipulation: I will subscribe ten dollars provided (on the condition ) that you do, too. Provided he goes, we can go along. Providing means the same as provided that is, just in case some certain thing should happen: We will buy the house, providing (provided ) we can get a mortgage.

If meaning “whether,” as in I haven't decided if I'll go, is sometimes criticized, but the usage has been established in standard English for a long time.
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Also, IF.
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
if (ɪf)
1.  in case that, or on condition that: if you try hard it might work; if he were poor, would you marry him?
2.  used to introduce an indirect question. In this sense, if approaches the meaning of whether
3.  even though: an attractive if awkward girl
4.  a.  used to introduce expressions of desire, with only: if I had only known
 b.  used to introduce exclamations of surprise, dismay, etc: if this doesn't top everything!
5.  as if as it would be if; as though: he treats me as if I were junior to him
6.  an uncertainty or doubt: the big if is whether our plan will work at all
7.  a condition or stipulation: I won't have any ifs or buts
[Old English gif; related to Old Saxon ef if, Old High German iba whether, if]

IF or electronics i.f.
abbreviation for
intermediate frequency
i.f. or electronics i.f.
abbreviation for

Collins English Dictionary - Complete & Unabridged 10th Edition
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Dictionary.com's 21st Century Lexicon
Main Entry:  IF
Part of Speech:  n
Definition:  See interactive fiction
Dictionary.com's 21st Century Lexicon
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Word Origin & History

O.E. gif (initial g- in O.E. pronounced with a sound close to Mod.Eng. -y-), from P.Gmc. *ja-ba (cf. O.N. ef, O.Fris. gef, O.H.G. ibu, Ger. ob, Du. of), probably originally from an oblique case of a noun meaning "doubt" (cf. O.H.G. iba, O.N. if "doubt"). Iffy is first attested 1937 in Amer.Eng.; originally
associated with President Franklin D. Roosevelt.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

IF abbr.
initiation factor

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Abbreviations & Acronyms
  1. infertility

  2. intracytoplasmic sperm injection

  3. interferon

  4. intermediate frequency

The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage
Idioms & Phrases


In addition to the idioms beginning with if, also see as if; damned if I do, damned if I don't; make as if to; no ifs or buts; nothing if not; (if) push comes to shove; what if.

The American Heritage® Dictionary of Idioms by Christine Ammer.
Copyright © 1997. Published by Houghton Mifflin.
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