The word 'word' is a singular, common noun. The word 'word' can be concrete (spoken, it's heard; written, it's seen) or abstract (as a kind word or a word to the wise).
yes... a gerund is a verb form but is used as a noun. example:
verb: writing. He will be writing the poem tomorrow. writing here is used a s verb.
gerund: writing. Writing songs is my hobby....