Is women's a plural noun

The Word women is a plural noun, the plural form of the singular noun woman.

The Word women's is the plural possessive noun. The apostrophe s ('s) is used to indicate possession, ownership, origin, or purpose.

Example:

This is a list of the women invited to the luncheon. (plural)

The women's luncheon is scheduled for the fourth of the month. (plural possessive, the luncheon for the women)