Sentence 1: Nouns, pronouns, verbs, adverbs, adjectives, prepositions, conjunctions and interjections are the 8 parts of speech.
Nouns: nouns, pronouns, verbs, adverbs, adjectives, prepositions, conjunctions, interjections, parts, speech
Verb: are
Determiner: the
Adjective: 8 (used as an adjective describing “parts”)
Sentence 2: Nouns, pronouns and verbs form the core of an English sentence.
Nouns: nouns, pronouns, verbs, core, English, sentence
Verb: form
Conjunction: and
Determiner: the, an
Sentence 3: Interjections should be avoided in formal writing.
Nouns: interjections, writing
Modal verb: should
Main verb: be (as part of passive “be avoided”)
Verb (past participle): avoided
Preposition: in
Adjective: formal