it makes the condition more restrictive

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.

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

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

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

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

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

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

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

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

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

if something should happen: