combine, couple, unite

a child / (figuratively) a girl, especially a dear or desired one (compare use of English baby, babe) / a smaller or younger version of a bigger object

an egg

an egg, including fish roe / the beginning or start of something (compare the uses of English terms kernel and seed) / a beginner or rookie at something

an ovum

behind, after

(spatially) the back, the rear, behind / (temporally) later, afterwards, some time after the present / the rest

one's backside / the back, the rear (both spatially and temporally)

the rear, back, or backside of something / the rearward or backward direction / the portion of a palace where a queen or other female imperial consort lives

later, afterwards, some time after the present