Questions & Answers about Я учу новый язык.
Why does the verb end in -у here instead of -ю?
The dictionary form of this verb is учить. For second conjugation verbs, the я (I) form usually ends in -ю. However, Russian has a strict spelling rule: you can never write the letter ю after ч. Because of this rule, the ending changes to -у, giving us я учу.
Does учу mean 'I learn' or 'I am learning'?
It means both! Russian only has one present tense. There is no separate 'am doing' tense like in English, so я учу can mean you learn generally, or that you are actively learning right now.
Новый язык is the object of the sentence. Shouldn't its ending change?
You are right that it is the direct object and needs the Accusative case. However, for masculine words that are inanimate (not alive), the Accusative form is exactly the same as the dictionary form. Since язык (language) is a masculine inanimate noun, новый язык doesn't change its spelling here.
I have also seen учить translated as 'to teach.' How do I know which meaning to use?
Context is your best clue. When учить is followed by a topic or a thing, like a language or a song, it means 'to learn.' If it is followed by a person (who is being taught), it generally means 'to teach.'