Buenos

Buenos is the masculine plural form of the Spanish adjective bueno, meaning "good." It agrees with masculine plural nouns, as in días buenos (good days) or amigos buenos (good friends). The feminine plural form is buenas, used with feminine plural nouns. In many phrases, buenos functions as part of common greetings or descriptions such as buenos días (good morning) and, more broadly, buenos días, buenas tardes, and buenas noches.

In Spanish orthography, buen shortens to buen before masculine singular nouns (for example, un buen día, un buen hombre), while bueno remains before feminine or plural forms. The standalone adjective buen appears in many compound expressions and idioms, and bueno/buen can be intensified in colloquial speech (e.g., un buen rato, una buena idea).

Geographically and culturally, the most famous use of the word is in Buenos Aires, the capital and largest city of Argentina. The name is commonly interpreted as "good airs" or "fair winds," reflecting a historical association with favorable winds and harbor conditions. The exact origin of the toponym is debated, but the two-word proper noun has become widely recognized in Spanish and global contexts.

As a basic building block of Spanish, buenos plays a central role in describing qualities of people, places, and things, and it serves as a key example of gender and number agreement in the language.