Are you after the plural of the abrevieation? (i.e. Mr becomes Messrs)...I'm not sure there is one for Prof.
Probably easier to use Professors
Bridges is the plural form of bridge.
professor
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
There is no plural form for the word, countries. This word itself is a plural.
"Groceries" is the plural form of "grocery."
The plural form of "meter" is "meters."
The plural form of the demonstrative pronoun 'that' is those.
The abbreviated form for professor is prof.
The plural form for the noun sergeant is sergeants; the plural possessive form is sergeants'.
It has no plural form.
The plural form of rung is rungs.
The plural form of parenthesis is parentheses.