Breakdown of Закрой окно, не то замёрзнешь.
окно
window
закрыть
to close
не то
or else
замёрзнуть
to freeze (turn to ice, feel cold)
Questions & Answers about Закрой окно, не то замёрзнешь.
What is the exact difference between не то and а то in warnings like this?
In this context, they are practically identical and fully interchangeable. Both mean "or else" or "otherwise" and are used to introduce a negative consequence. не то can sometimes sound just a tiny bit more colloquial or slightly more urgent, but you can safely use either.
Could I use иначе here instead of не то?
Yes, but it changes the tone slightly. иначе is the neutral, standard word for "otherwise". Using не то (or а то) makes the sentence more conversational and strongly emphasizes the warning or threat aspect: "do this, or else this bad thing will happen."
I've seen не то used to mean "either... or". How do I tell these apart?
Great catch! When used twice as a pair (не то ..., не то ...), it means "either ... or ..." but specifically when the speaker is guessing or uncertain (for example, "either snow or rain, I can't tell"). Here, it's used just once after a command, which signals it's the conjunction meaning "or else".
Why is there no ты (you) before замёрзнешь?
In conversational Russian, subject pronouns are frequently dropped when the verb ending makes the subject obvious. Since замёрзнешь has the 2nd-person singular -ешь ending and naturally follows the imperative Закрой (addressed to "you"), adding ты is unnecessary and sounds slightly less natural here.