The second person pronoun you is both singular and plural.
When speaking to one person, we say, "You seem happy today."
When speaking to a group of people, we also say, "All of you seem happy today."
In some regional dialects, the terms Y'all (a contraction of 'You all'), Youse (or "youse guys"), or You-uns("you"+"ones") can be used to indicate a plural 'You'.
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.
The plural form of the demonstrative pronoun 'that' is those.
Trenches is the plural form.
The plural form is metres.