(euphemistic) the world's oldest profession

world

the oldest

(colloquial) a girlfriend (a female partner in a romantic relationship)

(literary) they (about women or girls)

(formal) Female third-person singular pronoun; she, her, girlfriend

occupation, trade, profession, business

to research, to study

a piece of research, a study, investigation

world / a metaphorical world (how one lives one's life) / society, the times / a realm, a circle, a sphere / (Buddhism) the four inner realms of 須弥山 (Shumisen) / (Buddhism) realm governed by a buddha