what do u call it?

[Coffa]

Originally Posted by Philly

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I've even heard adults referred to as "the baby in the family".
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Maybe it's a BE vs AmE thing, but I think saying 'youngest male' or 'youngest female' sounds distinctly "clinical" (i.e. unnatural).

Well, OK Philly . Perhaps 'youngest son', or 'youngest daughter'.

[MrPedantic]

Additionally:

"Baby (of the family)" implies a certain familiarity with the person in question. You couldn't apply it in all cases.

I'm not sure many people would understand "Benjamin", these days. "Last born" might also be met with momentary bewilderment.

"Cadet" could once be used; but now the military connotations have obscured that particular meaning.

MrP