ἐάν;
I. a conditional particle (derived from εἰ ἄν), which makes reference to time and to experience, introducing something future, but not determining, before the event, whether it is certainly to take place; if, in case, (Latin si; German wenn; im Fall, dass; falls; wofern); cf., among others, Hermann ad Viger., p. 832; Klotz ad Devar. ii. 2, p. 450ff; Winers Grammar, 291f (273f). It is connected:
1. with the subjunctive, according to the regular usage of the more ancient and elegant classic writers.
a. with the subjunctive present: Matthew 6:22 (ἐὰν οὖν ὁ ὀφθαλμός σου ἁπλοῦς ᾖ, if it be the case, as to which I do not know, that thine eye etc.); Matthew 6:23; Matthew 17:20; Luke 10:6; John 7:17; John 8:54 [R G L marginal reading]; John 9:31; 11:9,10; Acts 5:38; Acts 13:41; Romans 2:25; 1 Corinthians 9:16; Galatians 5:2; 1 Timothy 1:8 [not Lachmann]; Hebrews 13:23; 1 John 1:9; 1 John 2:3, 15 etc.
b. with the subjunctive aorist, corresponding to the Latin future perfect: Matthew 4:9 (ἐὰν προσκυνήσῃς μοι, if thou shalt have worshipped me); Matthew 5:46; Matthew 9:21; Mark 3:24; Mark 9:50; Luke 14:34; Luke 17:4; Luke 20:28; John 5:43; John 11:57; Romans 7:2; Romans 10:9; 1 Corinthians 7:8, 39; 1 Corinthians 8:10; 1 Corinthians 16:10 (ἐὰν ἔλθῃ Τιμόθεος; for although he was already on his way to Corinth, yet some hindrance might still prevent his arriving); 2 Corinthians 9:4; Galatians 6:1; James 2:2; 1 John 5:16 [Lachmann present]; Revelation 3:20, and often; also in the oratio obliqua, where the better Greek writers use the optative: John 9:22; John 11:57; Acts 9:2 (Winers Grammar, 294 (276); [cf. Buttmann, 224 (193)]). The difference between the present and the aorist may be seen especially from the following passages: 2 Timothy 2:5 ἐὰν δὲ καὶ ἀθλῇ τις, οὐ στεφανοῦται, ἐὰν μὴ νομίμως ἀθλήσῃ, 1 Corinthians 14:23 ἐὰν οὖν συνέλθῃ ἡ ἐκκλησία... καὶ πάντες γλώσσαις λαλῶσιν, εἰσέλθωσι δὲ ἰδιῶται ἢ ἀπιστοι, 1 Corinthians 14:24 ἐὰν δὲ πάντες προφητεύωσιν, εἰσέλθῃ δέ τις ἄπιστος, Matthew 21:21 ἐὰν ἔχητε πίστιν καὶ μὴ διακριθῆτε. Also εἰ ("quod per se nihil significat praeter conditionem," Klotz, the passage cited, p. 455) and ἐάν are distinguished in propositions subjoined the one to the other [Winer's Grammar, 296 (277f)]: John 13:17 εἰ ταῦτα οἴδατε, μακάριοί ἐστε, ἐὰν ποιῆτε αὐτά, John 3:12; 1 Corinthians 7:36; in statements antithetic, Acts 5:38f; or parallel, Mark 3:24-26. Finally, where one of the evangelists uses εἰ, another has ἐάν, but so that each particle retains its own force, inasmuch as one and the same thing is differently conceived of by the different minds: Mark 9:43 ἐὰν σκανδαλίζῃ [-λίσῃ L marginal reading T WH text] ἡ χείρ σου, and Mark 9:47 ἐὰν ὁ ὀφθαλμός σου σκανδαλίζῃ σε, i. e. if so be that, etc.; on the other hand, Matthew, in Matthew 18:8f and Matthew 5:29f concerning the same thing says εἰ.
c. irregularly, but to be explained as an imitation of the Hebrew אִם which is also a particle of time (cf. Gesenius, Thesaurus, under the word, 4), ἐάν with the subjunctive aorist is used of things which the speaker or writer thinks will certainly take place, where ὅταν, when, whenever, should have been used: ἐὰν ὑψωθῶ, John 12:32; ἐὰν πορευθῶ, John 14:3; ἐὰν φανερωθῇ, 1 John 2:28 (L T Tr WH, for ὅταν R G); 1 John 3:2; ἐὰν ἀκούσητε, Hebrews 3:7 from Psalm 94:8 (Ps. 95:8); (ἐὰν εἰσέλθῃς εἰς τὸν νυμφῶνα, Tobit 6:17 (Tobit 6:16) [others, ὅταν]; ἐὰν ἀποθάνω, θάψον με, Tobit 4:3, cf. Tobit 4:4 ὅταν ἀποθάνῃ, θάψον αὐτήν; for אִם when, Isaiah 24:13; Amos 7:2).
d. sometimes when the particle is used with the subjunctive aorist the futurity of a thing is not so much affirmed as imagined, it being known to be something which never could happen: ἐὰν εἴπῃ ὁ ποῦς, if the foot should say, or were to say, 1 Corinthians 12:15; ἐὰν ἔλθω πρὸς ὑμᾶς γλώσσαις λαλῶν, 1 Corinthians 14:6.
2. By a somewhat negligent use, met with from the time of Aristotle on, ἐάν is connected also with the indicative [cf. Klotz, the passage cited, p. 468ff; Kühner, § 575 Anm. 5; Winers Grammar, 295 (277); Buttmann, 221f (191f); Tdf. Proleg., p. 124f; WHs Appendix, p. 171; Sophocles' Lexicon, under the word; Vincent and Dickson, Modern Greek, 2nd edition, Appendix, § 77]; and
a. with the future indicative, in meaning akin, as is well known, to the subjunctive: [ἐὰν δύο συμφωνήσουσιν, Matthew 18:19 T Tr]; ἐὰν οὗτοι σιωπήσουσι, Luke 19:40 L T Tr WH; ἐὰν... ὁδηγήσει, Acts 8:31 T Tr WH, (ἐὰν βεβηλώσουσιν αὐτά, Leviticus 22:9); but also
b. with the present indicative: ἐὰν δανείζετε, Luke 6:34 L marginal reading Tr text; ἐὰν στήκετε, 1 Thessalonians 3:8 T Tr text WH; ἐάν τε ἀποθνήσκομεν, Romans 14:8 Lachmann with an preterite indicative, but one having the force of a present: ἐὰν [Lachmann ἂν] οἴδαμεν, 1 John 5:15 without variant.
3. ἐάν joined with other particles;
a. ἐὰν δὲ καί, but if also, but even if, [A. V. but and if (retained by R. V. in 1 Cor.)]; with the subjunctive: Matthew 18:17; 1 Corinthians 7:11, 28; 2 Timothy 2:5.
b. ἐὰν καί: Galatians 6:1.
c. ἐὰν μή, if not, unless, except; with the subjunctive present: Matthew 10:13; Luke 13:3 [Lachmann text aorist]; Acts 15:1 [Rec.]; 1 Corinthians 8:8; 1 Corinthians 9:16 [R G L marginal reading T WH marginal reading]; James 2:17; 1 John 3:21; with the subjunctive aorist: Matthew 6:15; Matthew 18:35; Mark 3:27; John 3:3; John 8:24; 1 Corinthians 14:6f, 9; Romans 10:15; [Romans 11:23 R L]; 2 Timothy 2:5; Revelation 2:5, 22 [R L], and often with the indicative present: ἐὰν μὴ πιστεύετε, John 10:38 Tdf. In some passages, although the particles ἐὰν μή retain their native force of unless, if not, yet, so far as the sense is concerned, one may translate them, but that, without: Matthew 26:42 (the cup cannot pass by without my drinking. it); οὐ γάρ ἐστιν κρυπτόν, ἐὰν μή φανερωθῇ (Treg.), there is nothing hid, but that it shall be made manifest (properly, nothing whatever is hid, except that it should be made manifest), Mark 4:22; οὐδείς ἐστιν, ὃς ἀφῆκεν οἰκίαν... ἐὰν μὴ λάβῃ, but that shall receive (properly, unless he shall receive... it cannot be said that anyone has left), Mark 10:29, 30; [cf. Buttmann, § 149, 6. On the supposed use of ἐὰν μή (εἰ μή) as equivalent to ἀλλά, cf. Meyer on Matthew 12:4; Galatians 1:7; Galatians 2:16; Fritzsche on Romans 14:14 at the end; Ellicott and Lightfoot on Galatians, at the passages cited. See εἰ, III. 8 c. β.]
d. ἐάνπερ [L Tr separately, ἐάν περ] if only, if indeed: Hebrews 3:6 (where L brackets περ, and T Tr WH read ἐάν), Hebrews 3:14; Hebrews 6:3; it occurs neither in the Sept. nor in the O. T. Apocrypha; on its use in Greek writings cf. Klotz, the passage cited, p. 483f.
e. ἐάν τε... ἐάν τε, sive... sive, whether... or: Romans 14:8; (often in Sept. for אִם... אִם, as Exodus 19:13; Leviticus 3:1; Deuteronomy 18:3). Cf. Klotz, the passage cited, p. 479f; Kühner, § 541; [Buttmann, 221 (191)].
f. κἄν for καὶ ἐάν, see κἄν.
II. The classic use of the conditional particle ἐάν also in the contracted form ἄν (see p. 34^b above) seems to have led the biblical writers of both Testaments to connect ἐάν, with relative pronouns and adverbs instead of the potential particle ἄν, as ὃς ἐάν [so Tdf. in 12 places], ὃ ἐάν [so Tdf. uniformly], etc. (this use among secular writings is very doubtful, cf. Winers Grammar, p. 310 (291); Buttmann, 72 (63)): Matthew 5:19; Matthew 10:14 [R G]; Matt 15:5; Mark 6:22; Luke 9:48 [WH ἄν]; Luke 17:33; Acts 7:7 [R G T]; 1 Corinthians 6:18; Ephesians 6:8 [R G L text]; 3 John 1:5, etc.; ὅπου ἐάν, Matthew 8:19; Matthew 26:13; Mark 6:10 [L Tr ἄν]. ὁσάκις ἐάν, Revelation 11:6. οὗ ἐάν, 1 Corinthians 16:6 (1 Macc. 6:36). καθὸ ἐάν, 2 Corinthians 8:12 [Tdf. ἄν; ὅστις ἐάν, Galatians 5:10 T Tr WH; ἥτις ἐάν, Acts 3:23 Tdf. For many other examples see Sophocles' Lexicon, under the word, ἐάν, 3.] In many places the manuscripts vary between ἐάν and ἄν; cf. ἄν, II., p. 34; [and especially Tdf. Proleg., p. 96].

Related entry:

ἐάνπερ, see ἐάν, I. 3 d.