The nominative case is the “I” or “he/she/it” form of a noun/pronoun. For instance, in the sentence “I am going to the store,” “I” is the subject of the verb “am going” and is in the nominative case.
﻿The nominative case for pronouns that are the subject of a clause, as in “She is taller than I am.” In both cases, “she” and “I” are in the nominative case.
Finally, you can always use the nominative case for nouns and pronouns. That renames the subject of a sentence or clause, as in “My best friend, she loves animals.” Here, “my best friend” is in the nominative case and is renaming “she.”