Learn Russian: Ребёнок здесь? Нет, он не здесь, он там. - Is the child here? No, he is not here, he is there.

Нет means 'No' as a standalone answer to a question. Не means 'not' and is used to negate a specific part of the sentence. Following the rule for basic negation, не is placed right before the predicate здесь to mean 'not here'.

Why isn't there a word for 'is' in Ребёнок здесь or он не здесь?

In Russian, the present tense of the verb 'to be' (am, is, are) is usually skipped entirely. You just place the subject and its location next to each other, so Ребёнок здесь literally just translates word-for-word as 'Child here'.

Does the use of он mean the child is definitely a boy?

Not necessarily! The noun ребёнок (child) is a masculine word in Russian grammar. Because the word itself is masculine, we use the masculine pronoun он to refer back to it in the next part of the sentence, regardless of the child's actual gender.

How do you know Ребёнок здесь? is a question if the word order is exactly the same as a statement?

Unlike English, Russian doesn't require helper words (like 'do' or 'is') or flipped word order to make a yes/no question. You just take the normal statement and add a question mark. When speaking, you simply raise the pitch of your voice on the key word you are asking about, which is здесь.