Adjectives and adverbs are both modifiers.
(6) A preposition is a word placed before a substantive to show its relation to some other word in the sentence.
The substantive which follows a preposition is called its object.
(7) A conjunction connects words or groups of words.
(8) An interjection is a cry or other exclamatory sound expressing surprise, anger, pleasure, or some other emotion or feeling.
10. The meaning of a word in the sentence determines to what part of speech it belongs.
The same word may be sometimes one part of speech, sometimes another.
11. The infinitive is a verb-form which partakes of the nature of a noun. It is commonly preceded by the preposition to, which is called the sign of the infinitive.
12. The participle is a verb-form which has no subject, but which partakes of the nature of an adjective and expresses action or state in such a way as to describe or limit a substantive.
A participle is said to belong to the substantive which it describes or limits.