1. forsure;of certain:确定
2. must be:带有猜测的意味
3. of course:当然
不太清楚亲说的是什么意思下的一定，具体句子要具体分析，望采纳！谢谢！
一定要英语是
must
be sure to
definitely
surely
比如：
一定要做
must do
be sure to do
例句：
The tickets we must have by tomorrow in order to catch the plane
机票明天以前一定要有才能赶上飞机
Be sure to have this job done by tomorrow
这件事明天一定要办好
希望对你有帮助
你好，你是想表达 分开、分手那样的分别吗？这样翻译：
Separation is definite.
of course will It's totally will It's certainly will