If

• POS: Conjunction, Noun

CIDE DICTIONARY

If, conj. [OE. if, gif, AS. gif; akin to OFries. ief, gef, ef, OS. ef, of, D. of, or, whether, if, G. ob whether, if, OHG. oba, ibu, Icel. ef, Goth. iba, ibai, an interrogative particle; properly a case form of a noun meaning, doubt (cf. OHG. iba doubt, condition, Icel. if, ef, ifi, efi), and therefore orig. meaning, on condition that.].

•  In case that; granting, allowing, or supposing that; -- introducing a condition or supposition.  [1913 Webster]

  "Tisiphone, that oft hast heard my prayer,
  Assist, if Œdipus deserve thy care."  [1913 Webster]

  "If thou be the Son of God, command that these stones be made bread."  [1913 Webster]
•  Whether; -- in dependent questions.  [1913 Webster]

  "Uncertain if by augury or chance."  [1913 Webster]

  "She doubts if two and two make four."  [1913 Webster]

As if, But if. See under As, But.

OXFORD DICTIONARY

If, abbr. intermediate frequency.

If, conj. & n.
--conj.
1 introducing a conditional clause: a on the condition or supposition that; in the event that (if he comes I will tell him; if you are tired we will rest). b (with past tense) implying that the condition is not fulfilled (if I were you; if I knew I would say).
2 even though (I'll finish it, if it takes me all day).
3 whenever (if I am not sure I ask).
4 whether (see if you can find it).
5 a expressing wish or surprise (if I could just try!; if it isn't my old hat!). b expressing a request (if you wouldn't mind opening the door?).
6 with implied reservation, = and perhaps not (very rarely if at all).
7 (with reduction of the protasis to its significant word) if there is or it is etc. (took little if any).
8 despite being (a useful if cumbersome device).
--n. a condition or supposition (too many ifs about it).

Idiom

if only
1 even if for no other reason than (I'll come if only to see her).
2 (often ellipt.) an expression of regret (if only I had thought of it; if only I could swim!). if so if that is the case.

Etymology

OE gif

ROGET THESAURUS

If

Circumstance

N circumstance, situation, phase, position, posture, attitude, place, point, terms, regime, footing, standing, status, occasion, juncture, conjunctive, contingency, predicament, emergence, emergency, exigency, crisis, pinch, pass, push, occurrence, turning point, bearings, how the land lies, surroundings, context, environment, location, contingency, dependence (uncertainty), causation, attribution, circumstantial, given, conditional, provisional, critical, modal, contingent, incidental, adventitious, limitative, in the circumstances, under the circumstances, the circumstances, conditions, thus, in such wise, accordingly, that being the case, such being the case, in view of the circumstances, that being so, sith, since, seeing that, as matters stand, as things go, as times go, conditionally, provided, if, in case, if so, if so be, if it be so, depending on circumstances, in certain circumstances, under certain conditions, if it so happen, if it so turn out, in the event of, in such a contingency, in such a case, in such an event, provisionally, unless, without, according to circumstances, according to the occasion, as it may happen, as it may turn out, as it may be, as the case may be, as the wind blows, pro re nata, yet are my sins not those of circumstance.

Qualification

N qualification, limitation, modification, coloring, allowance, grains of allowance, consideration, extenuating circumstances, mitigation, condition, proviso, prerequisite, contingency, stipulation, provision, specification, sine qua non, catch, string, strings attached, exemption, exception, escape clause, salvo, saving clause, discount, restriction, fine print, qualifying, qualified, conditioned, restricted, hedged, conditional, exceptional, hypothetical, contingent, provided, provided that, provided always, if, unless, but, yet, according as, conditionally, admitting, supposing, on the supposition of, with the understanding, even, although, though, for all that, after all, at all events, approximately, in a limited degree (smallness), somewhat, sort of, something like that, to a certain extent, to a degree, in a sense, so to speak, with grains of allowance, cum grano salis, with a grain of salt, exceptis excipiendis, wind and weather permitting, if possible, subject to, conditioned upon, with this proviso, if the good lord is willing and the creeks don't r, catch-, Degrees of Evidence.

Supposition

N supposition, assumption, assumed position, postulation, condition, presupposition, hypothesis, blue sky hypothesis, postulate, postulatum, theory, thesis, theorem, data, proposition, position, proposal, presumption, divination, conjecture, guess, guesswork, speculation, rough guess, shot, shot in the dark, conjecturality, surmise, suspicion, sneaking suspicion, estimate, approximation (nearness), inkling, suggestion, hint, intimation, notion, impression, bare supposition, vague supposition, loose supposition, loose suggestion, association of ideas, (analogy), metonym, metonymy, simile (metaphor), conceit, idea, thought, original idea, invention (imagination), supposing, given, mooted, postulatory, assumed, supposititious, suppositive, suppositious, gratuitous, speculative, conjectural, hypothetical, theoretical, academic, supposable, presumptive, putative, suppositional, suggestive, allusive, if, if so be, an, on the supposition, ex hypothesi, in the case, in the event of, quasi, as if, provided, perhaps, for aught one knows.