if only和only if它们分别的用法和意思

if only: 要是...多好

Examples:
1. If only he had been here.
要是他当时在这儿就好了。
2. I dread the coming exams. If only I could have time to review my lessons.
我对即将到来的考试非常担心。如果我有时间复习该有多好啊。
3. If only I had another chance.
要是我再有一次机会就好了。
4. I am so tired. If only I can take the day off tomorrow.
太疲倦了。如果明天能不上班多好。
5. If only problems would come one at a time!
要是问题一次只发生一个该多好！
6. If only it clears up, we'll go.
只要天一放晴,我们就去。
7. If only one had an unlimited supply of money!
要是财源不断就好了！
8. She would be a very good player if only she could get it together.
她若能控制得当就能成为很好的选手.

only if:
conj. 只有当(只是在...的时候)

Examples:
1. The company will succeed only if it have sufficient backing.
只有当该公司获得足够的资助，它才会成功。
2. A compound proposition that has components joined by the word and or its symbol and is true only if both or all the components are true.