the usage of 除非 has been something i've been struggling with this week, so i thought i'd make a post reviewing it to help me get more practice with and confidence with it. 除非 is used to discuss hypothetical situations, as in "only if", "unless", etc. it can either be used by itself, or with other words in a part of a pattern.
除非 by itself is used in the second half of a sentence, giving a condition under which the first portion of the sentence can occur.
我每天上课, 除非我生病 "i go to class every day, unless i get sick" 每一门课有期末考试, 除非有个期末项目 "every course has a final exam, unless it has a final project" 图书馆的书都能带回家, 除非你要看特辑馆的书 "you can take any book from the library home, unless you want one from the special collections library"
when used at the start of a sentence paired with 否则/(要)不然 in the second half, it's used to express that unless the situation listed in the first portion of the sentence occurs, the second portion of the sentence holds true.
除非我把书弄坏, 不然我不会付破坏书费 "unless i damage the book, i won't have to pay the damaged book fee" 除非有免费的饮食, 否则我不会去一个聚会 "unless a gathering has free food, i won't go" 除非放假, 要不然留学的学生不会回家 "unless it's a break, study abroad students won't go home"
it's also paired with 才 to express that unless the first portion of the sentence occurs, the second portion of the sentence won't occur—essentially the inverse of the 除非......否则/(要)不然...... pattern.
除非有没有猪肉的选择, 她才会去餐厅吃晚饭 "if the dining hall has non-pork options, she will eat dinner there (otherwise, she will not)" 除非我有很早的预约, 我才在上午九点以前起床 "if i have an early appointment, then i will get up before nine in the morning (otherwise, i won't)" 除非你要养猫, 才能在这儿养宠物 "if you want to have a cat, then you can have a pet here (otherwise, you can't)"
