The plural possessive of "plane" is "planes'." This form indicates that something belongs to multiple planes, such as "the wings of the planes' are made of advanced materials."
The word swept is the past participle, past tense of the verb to sweep (He swept the floor.), and an adjective, a word that describes a noun (The plane had a swept wing.). There is no plural form for a verb or an adjective. Nouns and pronouns have plural forms.
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 "I" is "we."
The plural form of "was" is "were."
"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 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.
The plural form of the demonstrative pronoun 'that' is those.