Learn Turkish: Köpek nerede? O kaçıyor! - Where is the dog? It is running away!

The verb root is kaç (to run away). Since it ends in a consonant, we add the present continuous suffix. The vowel in kaç is 'a', so 4-way vowel harmony tells us to use -ıyor. Because the subject is 'it', we don't need to add an extra personal suffix at the very end.

Why use O for a dog? Doesn't O mean 'he' or 'she'?

In Turkish, O is a universal pronoun for the third-person singular. It means 'he', 'she', and 'it'! There is no separate gendered pronoun or a special word for 'it', so O works perfectly for the dog here.

Why is the word for 'where' nerede instead of just nere?

The base word nere just means 'what place'. To ask 'at what place' someone or something is currently located, we have to add the locative suffix -de (which means in, on, or at). So, nerede literally means 'at where'.

Does kaçıyor mean 'running' in general, like jogging in the park?

No, the verb root kaç specifically means to run away, flee, or escape. If the dog were just running around for fun or playing, you would use the regular verb for running (koşmak) and say koşuyor instead.