In this brilliant video you can find 5 ways of saying 'IF' without actually saying it.
"'If' is a word that is often used to introduce conditional sentences. It's not the only way though. In 90 seconds Dan demonstrates five different expressions that have the same or similar meaning to 'if'."
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Here's a new video from them teaching 5 ways of saying 'if' without actually saying it.
The explanations are easy-to-understand and the example sentences will definitely stuck in your head.
As long as = if and only if
'If we go on holiday, shall we go to Europe?'
'As long as we go somewhere hot, I don't mind'
'Oh, somewhere hot? Suppose we go to America. Would you like that?
Unless = if not/ except if
'Listen, unless I get a tan, I'll be really unhappy'
Providing, .... = if
'Providing you sunbathe a lot, you'll definitely get a tan'
On the condition = (formal, mostly used in written forms) if
'On the condition that I get time off from work, we'll go to America'