Occurring in sequence.
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se·quen·tial si-'kwen-chəl adj
1) occurring as a sequela of disease or injury
2) of, relating to, forming, or taken in a sequence <\sequential pills for contraception>
sequential n a birth control pill of which those taken during approximately the first three weeks contain only estrogen and those taken during the rest of the cycle contain both estrogen and progestogen
Medical dictionary. 2011.