(idiomatic) If need be; if there is a need.

(idiomatic) Used to suggest or state tentatively that something may be the case (often the opposite of something previously implied).

If something one wishes to be done cannot be commanded done, one must find another way to achieve one's goal.

Please, kindly; used in giving a non-concrete instruction. / So to speak, like; used to indicate that a description is not standard. / Used in conceding a description.

(colloquial, vulgar, humorous) It is fruitless to speculate about counterfactual situations.

It is better to do something oneself than to rely on others to do it well.

(informal) In an iffy manner.

Leave something alone; avoid attempting to correct, fix, or improve what is already sufficient (often with an implication that the attempted improvement is risky and might backfire).

(obsolete) Unless.

(informal, chiefly law) In the event that the thing being discussed comes to pass.