Learn Russian: Он мальчик? Нет, он не мальчик, а мужчина. - Is he a boy? No, he is not a boy, but a man.

Нет means "No" (the opposite of "Yes") and is used at the beginning to answer the question. не means "not" and is used to make a specific word negative. In Russian, не goes directly before the word it negates, which is why we say не мальчик to mean "not a boy".

Where is the word for "is" in this sentence?

In Russian, the present tense of the verb "to be" (am, is, are) is almost always left out. To ask "is he a boy?", you just say Он мальчик? (literally "he boy?"). To say he is not a boy, you simply add не before the noun: он не мальчик ("he not boy").

Why does the sentence use а for "but" instead of another word?

Russian has a few words that translate to "but", and а is used to show a direct contrast. It often follows a negative statement to mean "not this, but rather that". Since the sentence contrasts не мальчик (not a boy) with мужчина (a man), а is the perfect word to connect them.

The word мужчина ends in "а". Does that mean it is a feminine word?

No, мужчина (man) is a masculine word because it refers to a male person. Even though it has an ending typical for feminine words, grammatically it is masculine. That is why it makes perfect sense to talk about a мужчина using the masculine pronoun он (he).