The adjective modifies the noun and provides quality, state, relation, or precision about the named entity. In Spanish, its form usually agrees with the gender and number of the noun, as is the case with the [Nominal Gender] and [Nominal Number] systems. This agreement also affects several types of adjectives, including descriptive, demonstrative, possessive, and indefinite ones.

When the adjective distinguishes masculine and feminine, it adopts the gender of the noun it accompanies. This variation is visible especially in adjectives ending in o and in many nationality adjectives. Some adjectives, however, keep the same form for both genders and only change by number.

IdeaIdea	EjemploExample
El adjetivo cambia de género para concordar con el sustantivo.The adjective changes gender to agree with the noun.	Niño alto.Tall boy.
El femenino suele formarse con a en muchos adjetivos terminados en o.The feminine is usually formed with a in many adjectives ending in o.	Niña alta.Tall girl.
Algunos adjetivos tienen la misma forma en masculino y femenino.Some adjectives have the same form in masculine and feminine.	Estudiante inteligente.Intelligent student.
Muchos adjetivos de nacionalidad varían en género.Many nationality adjectives vary by gender.	Hombre español.Spanish man.
Algunos adjetivos de nacionalidad no cambian de forma.Some nationality adjectives do not change form.	Mujer inglesa.English woman.

The adjective also agrees in number with the noun and becomes plural when the noun is plural. Adjectives ending in e or in a consonant typically keep the same gender and only change in number. This rule is regularly applied in the majority of descriptive adjectives and in many participles used as adjectives.

IdeaIdea	EjemploExample
El adjetivo singular acompaña a un sustantivo singular.The singular adjective accompanies a singular noun.	Libro interesante.Interesting book.
El adjetivo plural acompaña a un sustantivo plural.The plural adjective accompanies a plural noun.	Libros interesantes.Interesting books.
Los adjetivos terminados en e cambian solo en número.Adjectives ending in e change only in number.	Alumna inteligente.Intelligent female student.
Los adjetivos terminados en consonante cambian solo en número.Adjectives ending in a consonant change only in number.	Estudiantes eficientes.Efficient students.
Los participios usados como adjetivos concuerdan con el sustantivo.Participles used as adjectives agree with the noun.	Puerta cerrada.Closed door.

Apocope refers to some adjectives losing part of their form when placed before a noun. This reduction mainly affects buen, mal, and gran, as well as certain forms such as primer, tercer, and cualquier, depending on the context. The use of these short forms is common in everyday language, though regional and register variation can occur, as is also the case in other adjectival uses of [Descriptive Adjectives].

IdeaIdea	EjemploExample
Buen aparece ante sustantivo masculino singular.Buen appears before a masculine singular noun.	Buen amigo.Good friend.
Mal aparece ante sustantivo masculino singular.Mal appears before a masculine singular noun.	Mal día.Bad day.
Gran aparece ante sustantivo singular.Gran appears before a singular noun.	Gran hombre.Great man.
Primer se usa antes de un sustantivo.Primer is used before a noun.	Primer intento.First attempt.
Tercer se usa antes de un sustantivo.Tercer is used before a noun.	Tercer lugar.Third place.

The adjective can go before or after the noun, and its position influences emphasis and sometimes meaning. Preposed, it can sound more value-laden, emphatic, or stylized; postposed, it usually describes the quality in a more objective or classificatory way. The exact distribution can vary by region and register, especially in literary or colloquial uses.

IdeaIdea	EjemploExample
El adjetivo antepuesto puede dar valor expresivo.The preposed adjective can give expressive value.	Gran hombre.Great man.
El adjetivo pospuesto suele describir la cualidad de forma directa.The postposed adjective usually describes the quality directly.	Hombre grande.Big man.
Algunos adjetivos cambian de sentido según la posición.Some adjectives change meaning depending on position.	Viejo amigo.Old friend.
La posición puede modificar el matiz estilístico.Position can modify the stylistic nuance.	Bella casa.Beautiful house.
El uso puede variar según la región y el registro.Usage may vary by region and register.	Palabra sencilla.Simple word.

Compound adjectives usually form the plural on the last part of the word. This pattern appears frequently in compound adjectives and in some scholarly or technical compounds. The agreement remains mandatory with the noun they modify, so the adjective retains the same gender and marks the number where appropriate.

IdeaIdea	EjemploExample
El plural suele marcarse en la última parte del compuesto.The plural is usually marked on the last part of the compound.	Socioeconómicos.Socioeconomic.
El compuesto concuerda con el sustantivo en número.The compound agrees with the noun in number.	Zonas socioeconómicas.Socioeconomic zones.
El adjetivo compuesto mantiene la concordancia de género.The compound adjective keeps gender agreement.	Proceso científico social.Social scientific process.
La forma plural afecta a la palabra final del compuesto.The plural form affects the final word of the compound.	Indicadores político económicos.Political-economic indicators.
Los compuestos se adaptan al sustantivo que acompañan.The compounds adapt to the noun they accompany.	Sistemas interrelacionados.Interrelated systems.

When a single adjective modifies two or more nouns, the agreement is plural. If the nouns have different genders, the usual form is masculine plural as the unmarked form of the group. When the sense of the whole is collective, the agreement may oscillate between singular and plural depending on semantic emphasis.

IdeaIdea	EjemploExample
Un adjetivo común a varios sustantivos va en plural.An adjective common to several nouns goes in the plural.	Juan y Ana están cansados.Juan and Ana are tired.
Si hay géneros distintos, suele usarse el masculino plural.If there are different genders, the masculine plural is usually used.	El padre y la madre están contentos.The father and the mother are happy.
La concordancia puede reflejar un sentido colectivo.The agreement can reflect a collective sense.	La familia está reunida.The family is gathered.
El plural marca que el adjetivo afecta al grupo completo.The plural marks that the adjective affects the whole group.	El libro y el cuaderno están nuevos.The book and the notebook are new.
La forma elegida depende también del sentido del hablante.The chosen form also depends on the speaker's sense.	El equipo está preparado.The team is prepared.

Participles that function as adjectives agree in gender and number with the noun. Therefore, a form like cerrado can appear as cerrada, cerrados, or cerradas depending on the noun it describes. This use relates to the description of state and to the formation of many derived adjectives.

IdeaIdea	EjemploExample
El participio se adapta al género del sustantivo.The participle adapts to the gender of the noun.	Puerta cerrada.Closed door.
El participio se adapta al número del sustantivo.The participle adapts to the number of the noun.	Puertas cerradas.Closed doors.
El participio puede funcionar como adjetivo descriptivo.The participle can function as a descriptive adjective.	Carta firmada.Signed letter.
La concordancia del participio sigue la del adjetivo regular.The participle's agreement follows that of the regular adjective.	Cajas abiertas.Open boxes.
El participio mantiene el valor de estado o resultado.The participle retains the state or result meaning.	Ventana bloqueada.Locked window.

Color adjectives usually agree in gender and number when they are simple forms like blue or red. Color compounds follow particular rules and often only pluralize the last part, especially when they function as a lexical unit. Some color names remain invariable, while others behave like regular adjectives.

IdeaIdea	EjemploExample
Azul cambia en número.Blue changes in number.	Camisa azul.Blue shirt.
Azul adopta el plural cuando el sustantivo también es plural.Blue takes the plural when the noun is also plural.	Camisas azules.Blue shirts.
Los colores simples suelen concordar como adjetivos regulares.Simple colors usually agree like regular adjectives.	Coches rojos.Red cars.
Los colores compuestos pluralizan la parte final.Compound colors pluralize the final part.	Tonos rojo oscuros.Dark red tones.
Algunos colores pueden tratarse como invariables según el uso.Some colors can be treated as invariable depending on usage.	Pantalón beige.Beige pants.

Adjective agreement brings together several decisions at once: gender, number, position, and, in certain cases, apocope or special pluralization. The adjective normally agrees with the noun, but its form can also depend on whether it modifies a single noun, several nouns, a participle, or a compound color. Mastering these guidelines allows you to use descriptive adjectives, demonstratives, possessives, and indefinite adjectives accurately in natural and varied contexts.