Vag is an anatomical feature of the structure of the female genitalia, expressed in the presence of a vagina (singular “vagina”). Vag was renamed from the Latin vulva. It is usually used as a derogatory name for that organ or when describing a situation involving that organ. In humans, the vagina is the vagina itself, not its opening.
Nowadays, the euphemism “vulva” is very common, which can be applied to either a separate organ or a structure without it. Vulva has synonyms