WORDS CLASSIFIED ACCORDING TO FORMATION

Root words
Derived[3]
Compound[4]

CLASSIFICATION OF WORDS ACCORDING TO INFLECTION

There are two kinds of words, thus considered: variable and invariable:

INVARIABLES: preposition
conjunction
interjection
They may be simple or compound, made up, that is, of one word or more.
VARIABLES: in gender and number nouns

may be of masculine, feminine, neuter or common gender.

form their plurals by adding -s or by changing the root vowel (umlaut)

in gender, number person and case pronouns

have special words for each form: e.g. he, him, who, whom, I, me, etc.

in degree adjectives
adverbs
-er for comparative
-est for superlative
in person, number, tense and mood verbs

show third person singular by adding -s, and old second person singular by adding -st

show moods by adding -ing, -ed or by vowel change for participles: or by special forms (I be, he be, etc.) for subjunctive.

show tense by suffix -ed, -t: or by vowel change (I go, I went).

show irregular forms.
for phonetic reasons definite article
indefinite

the has two pronunciations according to the following word.

a becomes an before a vowel.

CLASSIFICATION OF WORDS ACCORDING TO THEIR USE
(Parts of Speech)

ArticleVerbPronoun
NounAdverbConjunction
Adjective Preposition Interjection

Note: In actual usage the parts of speech perform not only their own functions, but also the functions of other parts of speech, for instance, the adjective, verb, adverb, conjunction, etc., may be used as nouns. The participles, etc., may be used as adjectives, or as clauses, etc.