From chamets; ferment, (figuratively) extortion -- leaven, leavened (bread).
see HEBREW chamets
H2557. chamets
חָמֵץ noun masculineExodus 13:3 that which is leavened — ֯׳ח 12:15 10t. — forbidden at Passover 12:15 (P), 13:3, 7 (JE), Deuteronomy 16:3, in all sacrifices Exodus 23:18; 34:25 (both J E); compare Amos 4:5; Leviticus 2:11; 6:10 (P; apposition); exceptions are ח ׳לֶחֶם of peace-offering 7:13 (P), and the wave-loaves (׳ח appositive) 23:17 (H). — see RSSem 208 OTJC 2, 345.
מַחְמֶ֫צֶת noun feminine anything leavened, only Exodus 12:19-20, (P).