If someone's name is williams and they are owning something is it williams' or williams's

What doe you mean someone’s name William

This is what i found “an elliptical clause is a type of dependent, or subordinate, clause that is missing a word or words. often, the missing part is a verb or verb phrase. while elliptical clauses are acceptable to use, they can sometimes cause confusion for writers and readers, especially when the sentence ends with a pronoun.” i hope this you for what your looking for. can you plz mark me brainliest?