To describe a person in Spanish - their personality and physical appearance - we use different adjectives. In Spanish, adjectives must agree with the number and gender of the noun or noun phrase. We do this by adjusting the ending of each adjective.
Feminine adjectives often end in -a (singular) or -as (plural) and masculine adjectives often end in -o (singlular) or -os (plural), but there are some special cases as explained below.
La muchacha = the girl. El muchacho = the boy.
El alumno = the male student. La alumna = the female student.
El profesor = the male teacher. La profesora = the female teacher.
El amigo = the male friend. La amiga = the female friend.
El chico es guapo. Los chicos son guapos. La chica es bonita. Las chicas son bonitas.
El hombre es feo. Los hombres son feos. Esa mujer es fea. Esas mujeres son feas. (feo, feos, fea, feas = ugly)
El alumno es pelirrojo. Los alumnos son pelirrojos. La alumna es pelirroja. Las alumnas son pelirrojas. (pelirojo, pelirrojos, pelirroja, pelirrojas = red-haired)
moreno/a, morenos/as = brunette
rubio/a, rubios/as = blond
delgado/a, delgados/as = thin
gordo/a. gordos/as = fat
bajo/a, bajos/as = short
alto/a, altos/as = tall
Describing personality in Spanish
Los Adjetivos para describir la personalidad de una persona