英和和英

not unknown

not known

unfamiliar

not made known

Who knows?

God knows.

unknown to most people

I know nothing

I do not know anything.

an unknown number

an unknown quantity

previously unknown

I don't know who it is.

not known to exist

not knowing anybody

not informed

to investigate and find out something for oneself

not knowable

lesser‐known

in a manner that is unclear

in ignorance

not recognized

anonymous

He is an utter stranger―a complete stranger―a perfect stranger―to me.

not known before

an unknown amount

I don't know his name or address.

I don't know anything about it whatsoever.

Address unknown

Don't understand anything