Is the world a singular or plural noun?

Answer 1

The proper noun "Earth" is singular, there is only one.

The common noun "earth" is an uncountable noun as a word for the soft or granular material composing part of the surface of the globe; a word for soil or clay; a word for a substance.

The plural common noun "earths" is a word specifically for "types of" or "kinds of" soil or clay.

Answer 2

The noun world is singular; the plural form is worlds. Example uses:

The world is getting smaller.

The worlds of fashion and commerce are joined at the hip.

Answer 3

The plural form of earth is earths.