Spanish adjectives have not only one form (like English). It's used in singular and plural, masculine and feminine, depending on the their noun.

Mi casa es pequeña./My house is small.
Mis perros son pequeños./My dogs are small.

Adjectives in Spanish usually come after their nouns:

Quiero un coche grande./I want a big car.

The participle can be used as an adjective: e.g. cerrado (closed)


The main kinds of adjectives are:

quality:

alto/tall
elegante/smart
malo/bad
corto/short

Demostrative:

este/this
ese/that
aquel/that
estos/these
esos/tose
aquellos/those

Distributive:

cada/each
todo/every
uno y otro/either
ni uno ni otro/neither

Quantitative:

algún/some
cualquier/any
poco/little
pocos/few
mucho/much
muchos/many
bastante/enough

Interrogative:

¿cual?/which?
¿qué?/what?
¿de quién?/whose?

Posesive:

mi/my
tu, su (de usted)/your
su (de él)/his
su (de ella)/her
su (de ello)/its
nuestro/our
vuestro/your
suyo (de ellos/as)/their

Owns:

inglés/English
español/Spanish
francés/French

Numerals:

uno/one
dos/two
primer/first
segundo/second