Yo is term used in london for a greeting.
"Yo what you sayin' fam"
Yo is very free, and morphable. Not a gen z word, such as rizz, or goofy ahh. But yo can be used like Yo. or yo? Such as Ay yooooo? When your friend says something sus.
Abbreviation for years old. 18 year old= 18-yo
I have an 18-yo daughter.