Definition:
ἐάν, contr. fr. εἰ ἄν, conditional particle, representing something as "under certain circumstances actual or liable to happen," but not so definitely expected as in the case of εἰ with ind. (Bl, §65, 4; cf. Jhn.13:17, 1Co.7:36), if haply, if; 1) with subjc. (cl.); (a) pres: Mat.6:22, Luk.10:6, Jhn.7:17, Rom.2:25, 26 al; { (b) aor. (= Lat. fut. pf.): Mat.4:9 16:26 (cf. ptcp. in Luk.9:25; M, Pr., 230), Mrk.3:24, Luk.14:34, Jhn.5:43, Rom.7:2, al; = cl. εἰ, with opt, Jhn.9:22 11:57, Act.9:2; as Heb. אִם = ὅταν, Jhn.12:32 14:3, I Jhn.2:28 3:2, Heb.3:7 " (LXX). 2) C. indic, (as in late writers, fr. Arist. on; see WH, App., 171; VD, MGr. 2, App., §77; Deiss, BS, 201f, LAE, 155, 254; M, Pr., 168, 187; Bl, §65, 4); (a) fut: Mat.18:19 T, Luk.19:40, Act.7:7; (b) pres: 1Th.3:8 (see Milligan, in l.). 3) With other particles: ἐ. καί (Bl, §65, 6), Gal.6:1; ἐ. μή (M, Pr., 185, 187; Bl, l.with), with subjc. pres, Mat.10:13, 1Co.8:8, Jas.2:17, 1Jn.3:21; aor, Mat.6:15, Mrk.3:27, Jhn.3:3, Rom.10:15, Gal.1:8 2:16 (see Lft, Ellic, in ll.); ἐ. τε. ἐ. τε, [in LXX for אִם. אִם, Est.19:13, al,] Rom.14:8. 4) = cl. ἄν (which see) after relat. pronouns and adverbs (Tdf, Pr., 96; WH, App., 173; M, Pr., 42f; Bl, §26, 4; Mayser, 152f; Deiss, BS, 202ff.): ὃς ἐ, Mat.5:19, Mrk.6:22, 23 Luk.17:32, 1Co.6:18, al; ὅπου ἐ, Mat.8:19; ὁσάκις ἐ, Rev.11:6; οὗ ἐ, 1Co.16:6; καθὸ ἐ, 2Co.8:12; ὅστις ἐ, Gal.5:10. (AS)