Buenas noches, abuela.

Good night, Grandma.

Breakdown of Buenas noches, abuela.

• la abuela: the grandmother
• buenas noches: good evening; good night

Questions & Answers about Buenas noches, abuela.

Why is it buenas and not buenos?

Because noches is a feminine plural noun.

• noche = night, evening
• noches = nights
• bueno/buena/buenos/buenas changes to match the noun

So:

• buenas noches = feminine plural
• buenos días = masculine plural
• buenas tardes = feminine plural

This is basic adjective agreement in Spanish.

Why is it noches in the plural if English says good night or good evening?

This is just how the fixed expression works in Spanish. Spanish uses the plural:

• buenos días
• buenas tardes
• buenas noches

Even though English often uses the singular, Spanish normally uses the plural in these greetings. You should learn buenas noches as a set phrase.

Does buenas noches mean good evening or good night?