61. Adjectives agree in gender and number with the nouns to which they relate.

una nueva pluma, a new pen.
nuevos libros, new books.

The plural of the adjective is formed exactly as is the plural of the noun. (See 25.) When the masculine singular of the adjective ends in -o, the feminine singular is formed by changing o to a.

alto, alta,
bueno, buena,

If the masculine singular does not end in -o most adjectives have the same form for both genders.

m. and f.
m. and f., poor.
m. and f.
m. and f., blue.

However, adjectives of nationality ending in a consonant, and adjectives ending in -án and in -or (not from a Latin comparative), add -a to form the feminine.

español, española españoles, españolas, Spanish.
holgazán, holgazana holgazanes, holgazanas, lazy.
traidor, traidora traidores, traidoras, treacherous.

62. Position of Adjectives. The adjectives in Spanish may precede or follow the noun. As a general rule, they follow the noun, especially in the case of long adjectives, proper adjectives, adjectives used emphatically, or of any adjective which is used to call attention to some individual object, separating it from other more or less similar objects.

un paisaje pintoresco, a picturesque landscape.
una casa blanca, a white house.
los libros españoles, the Spanish books.
el hombre bueno, the good man
(i.e., the man who is good).

a. Certain short, weak, much-used adjectives, and certain adjectives used merely for poetic effect precede the noun.

un buen niño, a good child.
un mal hombre, a bad man.
la blanca nieve, the white snow.

For emphasis, however:

un niño bueno.
un hombre malo.

b. Numeral adjectives and adjectives of quantity usually precede the noun.

tres libros, three books.
el segundo tomo, the second volume.
mucho dinero, much money.
poca carne, little meat.

63. Certain adjectives have two meanings, a literal meaning when they follow the noun, and a figurative or poetic meaning when they precede it.

un hombre pobre, a poverty-stricken man.
un pobre hombre, an unfortunate man.
un hombre grande, a big (tall) man.
un gran hombre, a great man.
mi tinta negra, my black ink.
mi negra suerte, my hard fate.

64. When a noun is limited by two or more adjectives the position of each is decided upon independently and according to the preceding rules. The last two of a series of adjectives are usually connected by the conjunction y.

Ha empleado un buen
secretario español.
He has employed a good
Spanish secretary.
blancos e inmovibles fantasmas, white and motionless phantoms.
un poblachón destartalado, antiguo, ruinoso e insufrible, an intolerable old town, neglected and in ruins.