In Latin est is singular. est plural is sunt
(Tu) est magister [male]/magistra [female].
Criteria is plural. Criterion is singular. Don't mess with Latin!
"You are" would be "es", if it is singular, or "estis", if it is plural.
A "Pilus" is the Latin for a hair, so following the Latin rules for plurals, the plural is "pili".
Alumna is a Latin word. (It is the feminine form of alumnus, plural alumni).And the feminine Latin plural of alumna is alumnae.
Tu (singular) Vos (plural)
The word "dicta" is a Latin plural. The singular is dictum.
Senex is singular in Latin and it means "old man" or "elder." The plural form is senes.
Tu (singular). Vos (plural).
Noli! (singular) Nolite! (plural)
Tu. (singular) Vos. (plural)
Salve! (singular) Salvete! (plural)