Alternatives to if

if something should happen:

an in case-clause gives a reason. We can use should after in case.

it can replace if in zero conditionals; in the other types of conditionals, we cannot use when instead of if.

It can interchangeably be used to mean "if - on condition that"

it makes the condition more restrictive

In formal situations, we can use if + were to when we talk about things that might happen but which we think are unlikely (imagiinary)

they can replace if, mainly in everyday conversation, and are often used without a main clause.

we can make the if-clause shorter, by omitting the subject and the verb be; in certain idiomatic expressions, the subject and be are normally omitted.

it emphasises that something will (or will not) happen, would (or would not) happen or would (or would not) have happened whatever the condition is/were.

these expressions mean without; they are used in second and third conditionals and are usually followed by usually precede a noun phrase.

we can use them instead of if to express a condition; note that providing/provided (that) is a bit formal.

it appears before an affirmative verb to express if … not.

Otherwise is used as a linking adverb and has the meaning of apart from this or if we disregard this: