There isn't a plural term for 'be'.
BE can only be used with a singular reference whether its used in future, current, or past tense.
BEEN; past tense of BE
Examples:
I will be a singer. I wanted to be a singer. I should have been a singer. I've been singing.
They will be early. They wanted to be early. They should have been early. They have been early on a few occasions
The plural of "she" is "they", so the plural of "she had" is "they had".
The plural of 'this' is 'these' and the plural of 'that' is 'those'.
Isthmi is plural. There are actually two plural forms. I will list them from singular to plural. Isthmus - Singular Isthmi - Plural Isthmuses - Plural
The plural of rose is roses. The plural possessive is roses'.
The plural form of can is cans.
Knights is a plural. It is the plural for knight.
applied is does not have a plural but is apply it does have a plural.
The plural is a regular plural, attics.
The plural of 'bunch' is bunches.The plural of 'ant' is ants.The plural of 'batch' is batches.The plural of 'day' is days.The plural of 'chimney' is chimneys.The plural of 'tomato' is tomatoes.The plural of 'umbrella' is umbrellas.The plural of 'donkey' is donkeys.The plural of 'sky' is skies.The plural of 'foot' is feet.The plural of 'show' is shows.
The plural for the noun loss is losses; the plural possessive is losses'.
pluralsThe word plurals is the plural of plural. As in: I answered the question about plurals to the person who didn't know that the plural of plural is plurals.
There is no plural for which