The plural form of 'ma and pa' is mas and pas.
Perhaps you're not old enough to remember The Mamas and The Papas folk rock group.
The plural of "ox" is "oxen".
The plural form for Harris is Harrises.
The plural of princess is princesses - just add "es." It's the same for prince: the plural is princes.
Only one way, F O X
The plural noun "sentries" is more than one sentry or guard. The similar plural noun "centuries" means periods of 100 years.
More than one blog=blogs.
Bills
The plural of woman is women.
The plural of "ox" is "oxen".
The plural form for Harris is Harrises.
The English plural is carcinomas. The Greek/Latin plural would be carcinomata.
The plural form of "scarf" is spelled "scarves."
Singular and plural are the same word - "series."
The plural of senior is seniors. The plural possessive is seniors' (referring to more than one senior).
The correct spelling of the plural of officer is officers.
The plural of buffalo is buffalo, buffaloes or buffalos. The preference is for buffalo.
Stimuli is the word you are looking for.