There is no feminine form. Senator is the word for both men and women equally.
Yes it is a noun.
The possessive form of the singular noun senator is senator's.Example: I got the summer job as a senator's intern.
Une personne (feminine noun)
The word "lentille" is a feminine noun in French.
"Actriz" is a feminine noun. "Actor" is the masculine.
"cette" means 'that' + feminine noun, or 'this' + feminine noun in French.
"la moquette", (feminine noun).
Oreille - ear, is a feminine noun. You can infer this by looking at how the noun is spelled -- it ends with "eille," which almost always indicates that it is a feminine noun.
Geraldine is the feminine for Gerald
Les Philippines is a feminine plural noun in French.
Marrant is masculine. The feminine version is 'marrante'.