Is longitude a proper or common noun?

Answer 1

The noun 'longitude' is a common noun, a general word for the imaginary lines that run between the North and South Poles to measure east-west position of the Earth.

A proper noun is the name of a specific person, place, or thing. The noun Earth is a proper noun, the name of a planet; the nouns North Pole and South Pole are proper nouns, the names of specific places.

Answer 2

Longitude is a common noun because it refers to a general concept or type of measurement rather than a specific or unique entity.