The plural form is briefs. Example sentences;
The lawyer submitted the briefs in court today.
I'll be leaving in an hour, my briefs are still in the dryer.
The plural of the noun brief (a legal summary) is briefs.
The plural is briefs. The plural possessive is briefs'.
If brief is used as an adjective, other words for it would include 'short' or 'succinct'. If used as a noun another word for it might be 'instructions'.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "was" is "were."
The plural form of "I" is "we."
The plural form of mouth is mouths. The plural form of month is months. The Mounth is a range of hills in Scotland and does not have a plural form.
"Groceries" is the plural form of "grocery."
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.