Abbott-Smith Manual Greek Lexicon
ἆρα (G687)
18 ἆρα , interrog. particle , implying anxiety or impatience, "quite rare and only in Luke and Paul, therefore a literary word" (Bl., §77, 2). ( num igitur ) expecting a neg. reply, Lk 18:8 ; ἆρά γε , Ac 8:30 . ( ergone ) in apodosis, expecting an affirm. reply, Ga 2:17 (Bl., §77, 2; Lft., Ga. , in l.; MM, s.v.).†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain