Singular possessives of nouns always use the apostrophe S regardless of their spelling.
The possessive would be genius's (e.g. a genius's IQ is very high).
Chat with our AI personalities
The plural possessive form is colonists'.
The possessive form for the noun colonist is colonist's.Example: A colonist's day was filled with hard work.
The possessive form of the noun historian is historian's.Example: The historian's presentation was very interesting.
spies
The possessive form of the singular noun yesterday is yesterday's.Example: There was an article about that in yesterday's newspaper.