Mistakes IS the plural form. The singular is mistake.
The plural form for the noun mistake is mistakes.
The form century's is the singular possessive form of the noun century.The plural form of the noun century is centuries.The plural possessive form is centuries'.example: Despite many centuries' passage, humans make the same mistakes over and over again.
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 "was" is "were."
The plural form of "I" is "we."
The plural form of "is" is "are."
"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.
Ah, a happy little question! The plural possessive for "star" would be "stars'." Just add an apostrophe after the "s" when showing that multiple stars own something. Remember, there are no mistakes, just happy accidents in grammar!