on; on top; upon; first (of two parts); previous or last (week etc); upper; higher; above; previous; to climb; to go into; above; to go up; to attend (class or university); third tone of putonghua[cedict]
然后
rán hòuㄖㄢˊ ㄏㄡˋ
after; then (afterwards); after that; afterwards[cedict]
受精
shòu jīngㄕㄡˋ ㄐㄧㄥ
to receive sperm; fertilized; insemination[cedict]