Mutatis mutandis
Is about the only Latinism that is genuinely tolerable, because it so succinctly captures a concept that English struggles to do accurately and briefly.
It means “as amended so the provision makes sense in the context in which you've just applied it”.
For example, say Bob and Joan have an agreement where a certain Event of Default applies to Bob only.
“It will be an Event of Default if Bob forgets to bring his lunch to school one day.”
And let’s say, for some reason (just go with me here) that Bob and Joan want that Event of Default to apply to Joan in one circumstance only. But only if Joan forgets to bring in her lunch (not Bob’s). If you’re the kind of soul — and most solicitors are — who thinks that isn't so face-slappingly obvious you don't need to say it, you might find mutatis mutandis can help.
“In circumstance X, the Event of Default will apply to Joan, mutatis mutandis.”
As ugly as this seems, it is better than:
“In circumstance X, the Event of Default will apply to Joan, as amended so the provision applies to Joan and her lunch, and not Bob and his lunch.”