Learn Spanish (Spain): Nunca he comprado unas botas caras. - I have never bought expensive boots.

He comprado is the present perfect tense, meaning "I have bought". In Spain, you use this tense to talk about life experiences when the exact time isn't specified. It is built using the helping verb haber (here, he for "I") plus the past participle (comprado).

If nunca means "never", why isn't there a no in this sentence?

In Spanish, if a negative word like nunca comes directly before the verb, you don't use no. You only use a double negative if the negative word goes after the verb. You could also say No he comprado nunca unas botas caras and it would mean exactly the same thing.

The English translation just says "expensive boots". Why is unas included here?

English often drops the article for plural nouns, but Spanish frequently uses unos or unas to mean "some" or "a pair of". Including unas makes the sentence sound more natural, as if you are saying "I have never bought a pair of expensive boots".

Why does the word caras come after botas?

In Spanish, descriptive adjectives like caras (expensive) almost always come right after the noun they describe. Because botas is a feminine plural noun, the adjective also has to match it, which is why it is spelled caras instead of the default masculine singular caro.