1
general::
if
used when talking about the possibility that something might happen or be true:
• He faces a long prison sentence if the court finds him guilty. • If scientists’ predictions are correct, average global temperatures could rise by 6 degrees.
unless
if something does not happen, or if someone does not do something:
• The star is difficult to see unless the sky is very clear. • Doctors said they could not treat the boy unless his parents gave their permission.
whether or not
used when saying that it does not matter if something happens or not, or if something is true or not:
• Most people will get better on their own, whether or not they receive medical treatment. • I’m still going, whether she likes it or not.
otherwise
used when saying that there will be a bad result if someone does not do something, or if something does not happen:
• Drink plenty of water – otherwise you will become dehydrated.
in case
in order to deal with something that might happen:
• She did not think it would rain, but she took her umbrella just in case. • It is best to keep a medical kit ready in case of emergency.
as long as/provided that
only if something else happens or is true:
• Visitors are welcome, as long as they bring their own tent. • Anyone can join the course, provided that there is space available. • As long as you can find a computer, you can access an internet-based bank account wherever you are.
on condition that
used when you agree to do something only if someone first agrees to do something else:
• He was offered the job on condition that he went on a month-long training course.
Longman-Thesaurus
3
general::
In addition to the idioms beginning with IF, Also see AS IF; DAMNED IF I DO, DAMNED IF I DON'T; MAKE AS IF TO; NO IFS OR BUTS; NOTHING IF NOT; (IF) PUSH COMES TO SHOVE; WHAT IF.
American Heritage Idioms