| Ending in -o | four forms: -o / -a / -os / -as | un libro blanco / unas casas blancas | a white book / some white houses |
| Ending in -e or a consonant | one form for both genders | un examen fácil / una pregunta fácil | an easy exam / an easy question |
| Nationality | a consonant ending adds -a for the feminine | un chico español / una chica española | a Spanish boy / a Spanish girl |
| Plural | -s after a vowel, -es after a consonant | verde → verdes / azul → azules | |
| Position | after the noun as a rule | un vestido rojo | a red dress |
| Mixed group | masculine and feminine nouns together take the masculine plural | Juan y Ana son simpáticos. | Juan and Ana are nice. |
| A2-or | adds -a for the feminine | una mujer trabajadora | a hard-working woman |
| B1buen / mal | bueno and malo drop -o before a masculine singular noun | un buen libro / un mal día | a good book / a bad day |
| B1gran | grande becomes gran before any singular noun and means great | una gran idea / un gran país | a great idea / a great country |
| Trap | the noun's gender decides, even when it ends in -a | el mapa nuevo | the new map |