繁衍fán yǎnto multiply; to reproduce; to increase gradually in number or quantity
敷衍fū yǎnto elaborate (on a theme); to expound (the classics); perfunctory; to skimp; to botch; to do sth half-heartedly or just for show; barely enough to get by
衍生yǎn shēngto give rise to; to derive; derivative; derivation
推衍tuī yǎnto deduce; to infer; an implication; same as 推演