Learn Spanish (Spain): Te esperé hasta las nueve.

In English, we 'wait for' someone, but in Spanish, the verb esperar already includes the 'for'. It directly takes an object. So, te esperé essentially means 'I awaited you'. You don't need to add por or para.

Why is esperé in the preterite tense here instead of the imperfect (esperaba)?

You use the preterite tense (esperé) because the action has a clear, specific endpoint in the past. By saying hasta las nueve (until nine), you are showing exactly when the waiting finished.

Why do we say las nueve instead of just nueve?

When telling time in Spanish, you always use a feminine article (la or las). This is because you are secretly referring to las horas (the hours), which is a feminine plural word, even though the word horas itself is left out.

If I wanted to say 'I waited for you at nine', would I still use hasta?

No, hasta specifically means 'until', showing a continuous action that stops at a certain limit. If you wanted to say you waited at nine o'clock, you would change the sentence to use the preposition a and say Te esperé a las nueve.