Not unless; used to introduce a necessary condition.
"only if" is a perfectly valid phrase to use in written English. You can use it to indicate that one thing will only happen if another thing also happens. For example, "I'll agree to the plan, only if we can make some adjustments first.".
If only, if only, if only.
Only if you are English.
But only if Iraq asks.
But only if done right.
Only if I say it.
And then, only if everything went perfectly.
But only if the weather cooperates.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.