[Footnote: "-aj" is pronounced like "ai" in "aisle". See 5.]

18. The article is invariable, that is, does not change in form when
used with plural nouns, as "la viro", the man, "la viroj", the men. The
verb is also invariable in form:

La viroj marsxas, the men walk, the men are walking.
La suno kaj la luno brilas, the sun and the moon are shining.
La viro estas, the man is.
La viroj estas, the men are.


PREDICATE ADJECTIVE AND NOUN.

19. When the adjective is a part of that which is told or predicated of
the subject of the verb, as when used with the verbs "to be," "to seem,"
etc., it is called a "predicate adjective":

La birdo estas bela, the bird is beautiful.
La knabo sxajnas bona, the boy seems good.
La viroj estas fortaj, the men are strong.

20. A noun may also be used as part of the predicate, and is then called
a "predicate noun":

Violoj estas floroj, violets are flowers.
La kolombo estas birdo, the dove is a bird.

21. Predicate nouns and adjectives agree in number with the word
or words with which they are in predicate relation: