Learn Turkish: İyi günler, ben öğretmenim.

In Turkish, many common greetings use the plural form to wish someone well, as if you are wishing them many good days. You will also see this plural pattern in iyi akşamlar (good evening) and iyi geceler (good night).

Do you use İyi günler to say hello or goodbye?

You can actually use it for both! It is very common to say iyi günler when you enter a shop or greet someone during the daytime, and you can also use it when you are leaving to mean have a good day.

Why isn't there a word for 'a' in ben öğretmenim?

When stating someone's profession in Turkish, you normally drop the word bir (a/an). You just attach the 'I am' ending directly to the profession. Adding bir sounds unnatural unless you are using an adjective, like if you wanted to say I am a good teacher.

Doesn't öğretmenim also mean 'my teacher'? How do we tell the difference?

Yes! The suffix -im is used both to mean 'I am' and to mean 'my'. You can tell them apart by looking at the context of the sentence. Because this sentence uses the subject pronoun ben (I) instead of the possessive pronoun benim (my), we know it means I am a teacher.