The difference between Century and Yearhundred

Century as a noun:

A period of 100 consecutive years; often specifically a numbered period with conventional start and end dates, e.g., the twentieth century, which stretches from (strictly) 1901 through 2000, or (informally) 1900 through 1999. The first century AD was from 1 to 100.

Century as a noun:

A unit in ancient Roman army, originally of 100 army soldiers as part of a cohort, later of more varied sizes (but typically containing 60 to 70 or 80) soldiers or other men (guards, police, firemen), commanded by a centurion.

Century as a noun:

A political division of ancient Rome, meeting in the Centuriate Assembly.

Century as a noun:

A hundred things of the same kind; a hundred.

Century as a noun (cricket):

A hundred runs scored either by a single player in one innings, or by two players in a partnership.

Century as a noun (sports):

A race a hundred units (as meters, kilometres, miles) in length.

Century as a noun (US, informal):

A banknote in the denomination of one hundred dollars.

Yearhundred as a noun (very, _, rare, nonstandard):

A period of a hundred consecutive years; a century.