Millennia.
The word comes from Latin. Some Latin words ending in -umin the singular change to -a in the plural.
Another example is bacterium. If you chance upon a whole group of them, they're bacteria!
New: The declension of these words would be second; the neuter (genderless) form would, in Latin, end in -i, but bacterium, which apparently is feminine, would end in -a.
The suffixes (Nom, Gen, Dat, Acc, Abl) for neuter and feminine are (Singular-Plural)
-us -i
-i -orum
-o -is
-um -os
-o -is
and feminine
-um -a
-i -orum
-o -is
-um -a
-o -is
Millennial is an adjective and doesn't have a plural. The noun it is based upon is millennium. The word millennium can be made plural in two ways that are equally acceptable. You can use millennia, which follows the Latin rule for plural, or you can use millenniums, which is the standard English form of plural. For fun, you can think of millennia as being a bit more academic or highbrow, and millenniums as being more hip. If you use millenniums and someone tells you it is an error, you can reply with "Yes, yes, I know the Latin. We are speaking English here..."
The plural form of the noun century is centuries.
The word centuries is a noun. It is the plural form of the noun century.
Bridges is the plural form of bridge.
The noun workforce is singular and takes a singular verbThe plural form is 'workforces'.Examples:The workforce at the plant is on strike. (singular)Most of the workforces of the nineteenth century were in agriculture. (plural)
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
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'.
The plural form of the noun century is centuries.
Centuries' is the plural possessive of the singular noun century.
The word century's is the possessive form of the singular noun century.The plural noun is centuries.The plural possessive form is centuries'.Example: Several centuries' records were destroyed in the war.
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.
Centuries' is the plural possessive of the singular noun century.
The word centuries is a noun. It is the plural form of the noun century.
The noun wars is the plural form of the singular noun war.The singular possessive form is war's.The plural possessive form is wars'.Examples:Our city was in ruins by the war's end. (singular)The wars' cost in lives in the twentieth century should never be repeated. (plural)
The plural form of "do" is "do" and the plural form of "don't" is "don't." These words do not change in the plural form when used in a sentence.
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The noun workforce is singular and takes a singular verbThe plural form is 'workforces'.Examples:The workforce at the plant is on strike. (singular)Most of the workforces of the nineteenth century were in agriculture. (plural)