According to their meaning, morphological characteristics and syntactical functions, words fall under certain classes called parts of speech.
We distinguish between notional and structural parts of speech. The notional parts of speech perform certain functions in the sentence: the functions of subject, predicate, attribute, object, or adverbial modifier.
The notional parts of speech are:
(1) the noun;
(2) the adjective;
(3) the pronoun;
(4) the numeral;
(5) the verb;
(6) the adverb;
(7) the words of the category of state;
(8) the modal words;
(9) the interjection.
The structural parts of speech either express relations between words or sentences or emphasize the meaning of words or sentences. They never perform any independent function in the sentence. Here belong: