buen

Buen is the masculine singular pre-nominal form of the Spanish adjective bueno. It is used directly before a masculine singular noun to express “good” in attributive position, typically replacing the full form bueno when the noun follows immediately and without an article. For example: buen día, buen libro, buen amigo. When used with an article, the standard forms apply: un buen día, un buen libro, un buen amigo.

The form buen agrees with gender and number of the noun: buena before feminine singular nouns (una buena idea), buenos before masculine plural nouns (buenos días), and buenas before feminine plural nouns (buenas ideas). The usage of buen is restricted to masculine singular nouns in attributive position; the feminine and plural forms are separate adjectives (buena, buenos, buenas).

Etymology traces buen to the adjective bueno, which derives from Latin bonus. Over time, buen emerged as the contracted pre-nominal form used for phonetic and stylistic reasons in Spanish. It is common across dialects and widely used in everyday speech, formal writing, and fixed expressions such as buen provecho (enjoy your meal) or buen viaje (have a good trip). In many idiomatic phrases, buen appears without an accompanying article and can precede proper names in rhetorical contexts, though it is not a standalone proper noun.

Overall, buen is a concise, widely used grammatical form that mirrors the gender and number agreement rules of Spanish adjectives, functioning specifically as the masculine singular pre-nominal variant of bueno.