Brown-Driver-Briggs (BDB)
H518a
H518a אִם conj . . hypoth. part . if . Interrog. part . H518b 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
Brown-Driver-Briggs Hebrew Lexicon (BDB), 1906 — public domain