At an introductory level, a ṣīghah is a word form; an ism (noun) names a person, object or concept, and a fiʿl (verb) conveys an act or state linked to time.
Word / formMeaning / explanation
زَيْدٌa person's name; noun.
كِتَابٌbook; noun.
كَتَبَhe wrote; verb.
Nouns and verbs are both words, but not every word is a verb. Morphology examines forms of both; understanding verbal forms especially requires attention to time.