Learn Turkish: Bu belgesel çok öğreticiydi. - This documentary was very instructive.

The root is the verb öğretmek (to teach). We add the suffix -ici, which derives an adjective or noun from a verb to describe someone or something that performs the action. So, öğretici means "instructive" or "educational." Finally, we add the past tense copula -di with a buffer -y- since the word ends in a vowel, making it öğreticiydi (it was instructive).

The suffix -ici often creates nouns for people who do an action. Can öğretici mean "teacher"?

While the suffix -ici frequently creates agent nouns (like izleyici for "viewer" or satıcı for "seller"), the established word for the profession of a teacher is öğretmen. Because of this, öğretici is almost exclusively used as an adjective meaning "instructive" or "informative," just as it is used here to describe the documentary.

Where does the word belgesel come from?

It is formed from the noun belge, meaning "document." The suffix -sel / -sal creates adjectives related to a noun, similar to "-al" or "-ic" in English (for example, tarihsel means "historical"). While it originally acts as an adjective, belgesel is now heavily used as a standalone noun for documentary films.

Why is there a -y- before the past tense suffix in öğreticiydi?