Most feminine adjectives end with the letter “a”. Most masculine adjectives end with the letter “o”.

For example:

atrevida (f. adjective)/ daring
atrevido (m. adjective/ daring

a, o

Adjectives that can be either masculine or feminine may end with the letters “es” (as in the word interesante/ interesting) or the letter “e” (as in the word interesante)

es, interesantes, e, interesante

The two singular definite articfles are “el” and “la”.
The stow singular indfeinite articles are “un” and “una”

el, la, un, una

In Spanish, adjectives come after the nouns they describe.

Un profesor inteligente. / A smart teacher.
Note that the adjective (inteligente) comes after the noun it describes

after