Learn Turkish: O yaramaz bir kediydi, evde topu kovalardı. - He was a naughty cat; he used to chase the ball in the house.

This is the habitual past, which combines the aorist (broad/simple present) tense suffix with the past tense suffix. The verb stem is kovala- (to chase). Since it ends in a vowel, we just add -r for the aorist, followed by the past tense suffix -dı, giving us kovalardı (used to chase / would chase).

Why is bir placed after yaramaz instead of before it?

In Turkish, when an adjective describes a noun with the indefinite article "a" or "an", the word bir usually comes between the adjective and the noun. So "a naughty cat" translates to yaramaz bir kedi (literally: naughty a cat). If you said bir yaramaz kedi, it would sound more like "one naughty cat".

Why is there a 'y' in kediydi?

The base word is kedi (cat). To say "was a cat", we need to add the past tense suffix -di. Because kedi ends in a vowel, we must insert the buffer letter -y- to smoothly connect the word and the suffix, making it kediydi.

Why does the sentence use topu instead of just top?

The suffix -u in topu is the accusative case marker, which makes the direct object specific. It shows that the cat used to chase the ball (a specific, known ball). If the sentence just said top kovalardı, it would mean the cat chased balls in general.