Learn Turkish: Köpek ürkek ama henüz hırlamadı. - The dog is timid, but it hasn't growled yet.

Turkish doesn't have a direct equivalent for the English present perfect tense (has/have done). Instead, when you combine henüz (yet) with a verb in the simple past negative like hırlamadı (didn't growl), it perfectly expresses the idea of "hasn't growled yet."

Does henüz always mean "not yet", or can it be used in positive sentences too?

In this sentence, henüz means "yet" because the verb hırlamadı is negative. If you use henüz with a positive verb instead, it changes meaning to "just" or "recently" (for example, henüz geldi means "it just arrived").

Is the adjective ürkek (timid) built from a verb?

Yes, it comes from the verb ürkmek, which means "to be spooked" or "to be startled". The suffix -ek (or -ak) is often added to verbs to create adjectives describing a habit or tendency, making ürkek mean a creature that easily gets spooked.

Hırlamak (to growl) sounds like the noise a dog makes. Is that a coincidence?

Not at all! Turkish uses onomatopoeia (words that imitate sounds) very often. Hır is the sound a dog makes when growling. By adding the verb-making suffix -la, you get hırlamak (to make a growling sound).