The word 'Gravity' is---- ?

The word "gravity" is classified as a noun because it denotes a specific concept or phenomenon rather than expressing action, description, or state. In linguistic terms, a noun is a word that identifies a person, place, thing, or idea. In this case, "gravity" refers to the force that pulls objects toward each other, most commonly the attraction between the Earth and other bodies, such as the moon or an apple falling from a tree.

To clarify the other options:

- A gerund (Option A) is a verb form ending in -ing that functions as a noun, such as "running" in "Running is fun." However, "gravity" does not fit this description.
- A verb (Option B) expresses action or a state of being, such as "run" or "is," which "gravity" does not represent.
- An adjective (Option C) describes a noun and often answers questions like "What kind?" or "Which one?". Words like "gravitational" would be adjectives, but "gravity" itself is not used in that context.

Thus, the classification of "gravity" as a noun is consistent with its usage and meaning, making D the correct answer.