One of the don'ts is as follows.
1. Don't say bad words.
1-1. Don't use bad words.
2. Don't use bad language.
2-2. Don't say bad language.
3. Don't swear.
4. ___________
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Are they all grammatical? Do you have other similar expressions?
2-2 is not correct. It is grammatical, but not like anything we would say or write.
I'm sure there are other ways of saying this, but I can't think of any. Some say, "Don't take the Lord's name in vain." Some say, "Don't use four-letter words".
Thank you....
4. Don't use filthy language.
5. Don't say filthy language.
6. Don't use a filthy language.
(Is #5 or #6 wrong?)
Yeah
#5 is not completely incorrect, but it sounds a bit unnatural. It would be better to say "Don't use filthy language" or "Don't use vulgar language".
#6 is not grammatically incorrect, but it's not a common way to express that idea.