Son?

[Caran]

Why is it ok to say "how are you son" when you wouldn't say "how are you daughter". Or OK son,

[Jackdaw33]

Because son is used to address any boy or young man. Daughter is specific.

[Mamyalynne]

One of the definitions of Son

Used by an older person as a form of address for a boy or young man.
‘you're on private land, son’

[Mamyalynne]

Sorry Jack, I should have refreshed the page.

[JimF]

Look across the mirror, sonny, before you choose decide

[Theland]

Why not, ''O.K.'' to say daughter, or anything else?
Who says?
There are no rules.
Do you understand that son/mate/daughter/love/lovely/darling/cuzz/ orlicks/ sis?

[Mamyalynne]

I understand what Caran means, you wouldn't say to a random young woman - ‘you're on private land, daughter’, simply because 'daughter' doesn't have that similar generic definition.

[bunkmoreland]

It probably depends where people are living. I've been referred to as daughter before,an Irish type thing said in a friendly manner:-)

[Jackdaw33]

When the name is not known I use young man/young lady. With people of riper years it's sir/madam.