Learn Turkish: Yoksul aileler bazen korkutulurdu. - Poor families would sometimes be frightened.

We start with the root kork- (to fear). First, we add the causative suffix -ut to make korkut- (to frighten or to make someone fear). Then we add the passive suffix -ul to make korkutul- (to be frightened). This is a great example of a causative-passive chain!

What tense is the -urdu ending on korkutulurdu?

It is a combination of the aorist (broad tense) suffix -ur and the past tense suffix -du. Together, they create the habitual past. In English, this translates to 'would be' or 'used to be' for an action that happened repeatedly in the past.

Why does the root kork- take -ut for the causative instead of the usual -t or -dir?

Causative suffixes can take a few different forms. Because kork- ends in a consonant, it cannot take just -t. It takes the -It form, which becomes -ut to follow the 4-way vowel harmony rules after the back, rounded vowel 'o'.

Since the subject is aileler (families, plural), why doesn't the verb end in the plural suffix -lar?