Buenas tardes, profesor.

Good afternoon, teacher.

Breakdown of Buenas tardes, profesor.

• el profesor: the teacher
• buenas tardes: good afternoon

Questions & Answers about Buenas tardes, profesor.

Why is it buenas and not buenos?

Because tardes is a feminine plural noun, and the adjective has to agree with it.

• bueno = masculine singular
• buena = feminine singular
• buenos = masculine plural
• buenas = feminine plural

So:

• buenas tardes = correct
• buenos tardes = incorrect

This is one of the most common agreement patterns in Spanish.

Why is tardes plural if English says good afternoon in the singular?

This is just how the expression works in Spanish. Buenas tardes is a fixed greeting, and Spanish uses the plural form here.

Compare:

• buenos días
• buenas tardes
• buenas noches

You should learn these as complete set phrases rather than trying to translate them word for word from English.

What part of the day does buenas tardes cover in Latin America?