Brown-Driver-Briggs (BDB)
H3588a
H3588a כִּי that , for , when . that . . Of time, when , of the past . elsewhere כִּי has a force approximating to if , though it usu. represents a case as more likely to occur than אִם . when or if , with a concessive force, i.e. though . Because , since H3588b כִּי אם־ . each part. retaining its independent force, and relating to a different clause: . that if . for if . (About 140 t.) the two particles being closely conjoined, and relating to the same clause— . limiting the prec. clause, except . the if being neglected, and treated as pleonastic, so that the clause is no longer a limitation of the preceding clause but a contradiction of it: but rather , but . after an oath, surely H3588c כִּי עַל כֵּן forasmuch as
Brown-Driver-Briggs Hebrew Lexicon (BDB), 1906 — public domain