[user104658]

I literal terms yes however I think 21 is a more sensible age to consider someone an actual adult - whilse still treating them like an adult from 18. I think that second part is vital TBH, because part of the reason I'd say 21 for measuring someone by the standards of a "full adult" is that they have been, for want of a better term, then been "living as an adult" for 3 years so they are an adult with ... experience of adulting.

Expecting someone to suddenly at 18 have the adult life experience to make reasonable adult decisions is insane. How? With what knowledge base?

BUT you have to keep 18 as the legal adult age, so they people DO get that experience of "somewhere between teen and adult" before they get into their early 20's... at which point it's then reasonable to expect people to stop acting like teenagers.

Otherwise you just end up with 20 year old teenagers, and "proper adulting" beginning at 24, and so on and so on.

FWIW if we're talking about in the context of Big Brother and other similar reality shows (Love Island et al) - I do think it should be 21 to apply.