Buenas tardes, profesor.

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.

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.

In most of Latin America, buenas tardes is used from around noon or after lunch until evening, before it becomes night.

A very general guide is:

• buenos días = morning
• buenas tardes = afternoon / early evening
• buenas noches = night

The exact timing can vary a little by country, region, and season, but this is the standard idea.

Because profesor is being used as a direct address (also called a vocative). You are speaking to the professor, not talking about him.

So Spanish separates it with a comma:

• Buenas tardes, profesor.

This is similar to English punctuation in:

• Good afternoon, professor.

In Spanish, titles like profesor, doctor, and señor are usually not capitalized unless they are part of a formal abbreviation or certain official styles.

So in normal writing:

• Buenas tardes, profesor.
• Hola, doctora.

This is different from English, where learners may be tempted to write Professor with a capital letter in direct address.

Not exactly. In Spanish, profesor is broader than English professor.

It can mean:

• a school teacher
• a high school teacher
• a university instructor

So a student might naturally say profesor to many kinds of teachers, not only a university professor in the English sense.

Then you would say:

• Buenas tardes, profesora.

The noun changes to match the person’s gender:

• profesor = male teacher
• profesora = female teacher

This is very important in Spanish because nouns referring to people often change form based on gender.

Yes, absolutely. Buenas tardes works perfectly well on its own as a greeting.

Adding profesor just makes it more specific and polite because you are directly addressing the teacher.

So both are natural:

• Buenas tardes.
• Buenas tardes, profesor.

Yes. Buenas tardes, profesor sounds polite and appropriate in a respectful situation, such as speaking to a teacher.

It is more formal than:

• Hola, profesor.

Both are possible, but buenas tardes sounds more courteous and a bit more professional.

A simple pronunciation guide is:

BWEH-nas TAR-des, პრო-feh-SOR

A few key points:

• bue in buenas sounds roughly like bweh
• tardes has a clear r and d
• the stress is on TAR in tardes
• the stress is on the last syllable of profesor: -sor

In standard Spanish pronunciation:

• Buenas → BWEH-nas
• tardes → TAR-des
• profesor → pro-fe-SOR

No. When you are directly addressing someone, you do not use the article.

So:

• Buenas tardes, profesor. = correct
• Buenas tardes, el profesor. = incorrect in this context

You would use the article only when talking about the teacher, for example:

• El profesor llegó temprano. = The teacher arrived early.

Yes, in many places profe is a very common and natural short form of profesor/profesora.

• Buenas tardes, profe.

This sounds friendly and normal in much of Latin America, especially in everyday school settings. However, profesor may sound a little more formal or respectful, depending on the situation and local custom.