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It is called pyromania. The person is a pyromaniac, or firebug.
A word that substitutes for a noun is a pronoun, which must match the noun in person, number, gender. This is called pronoun-antecedent agreement.
penniless
bookworm
Examples of synonyms for the word 'pronoun' are word or substitute.
A bibliophile loves books
what word can I substitute for constitutes
The word is optimist.(A person who is negative is a pessimist.)
An invalid
The word is busybody.
One word is reprobate.
The word could be "nitpicker."
masochist
An eavesdropper.
Commendation
Normally it is an administrator or manager.
The person would be inquisitive or curious.