Is the word "Lingo" appropriate in a formal context?
It sounds much more professional to me than "jargon", but I still have it in the back of my mind that it is slang.
Is there a synonym that would be better?
Learn English – Is “Lingo” appropriate in a formal context
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Best Answer
(a) Lingo is pretty dated (80s wealthy would-be hipsters, and people who pine for the British Empire being the only ones I have heard using it).
(b) It's kind of racist (it's dismissive of the manner of speech it is applied to), and it doesn't just mean "jargon", it means any manner of speech, including foreign language or other dialect one wishes to dismiss.
(c) There is absolutely no way it is more professional than "jargon" (which is a perfectly normal word).
The real question is why you think there might be a problem with using the word "jargon".