Unless is used as a conjunction to indicate the condition of something not happening or not being true, typically used in the middle of a sentence. For example 'We will go outside, unless it is raining.' In this sentence the adverb 'unless' expresses the condition that something is not happening (in this case, going outside) when another situation is true ('it is raining').
it is used in the middle of a sentence after a comma, or at the beginning of the sentence.Common mistakes include misusing the conjunction by attempting to use it at the end of a sentence, or changing the sense of the word intended by using surrounding words with the opposite meaning.
1. 'We will go outside, unless it is raining.'
2. 'Unless he changes his attitude, I don't think things will work out.'
3. 'Unless she pays the bill, she will not be able to leave the restaurant.'
Be aware when using 'unless' in conjunction with the phrase 'if not' that it could potentially change the intended meaning. For example, consider the sentence, 'Unless it is sunny, we can't go outside' compared to the sentence 'If it is not sunny, we can't go outside.' While the first sentence implies that if it isn't rainy, then we can go outside, the second sentence implies that if it isn't sunny, then we can't go outside.