The superficial trappings of something are unrelated to its true essence.

(often ironic, sarcastic) Don't blame yourself for the end of our relationship.

(now rare, archaic) Introducing a subordinate clause, frequently with that: "it is not that (the following clause) is not the case".

Used to indicate that the following clause is not true and that this negatively impacts the importance of the preceding clause.

(Scotland, law) Having insufficient evidence to prove guilt or innocence under Scots law.

Not the first time one has been in a particular situation; used to indicate past experience.

For an extremely good reason. / Used to soften the impact of what is said next, implying that it is important. / Used other than figuratively or idiomatically: see not, for, nothing.

Synonym of no longer

To be confused about how to handle a situation.

people who dispute that a task is possible should not impede those people who attempt to do it