Interested in Language
Between 'against' and 'off', which do you think best collocates with the verb 'warn'?
I warned them against/off swimming in a bay full of sharks.
I vote for 'against'.
Thank you for commenting.
I agree with Mike and Rover, and would add that in AE you're just as likely to hear "warned them about..." in which case the action you're warning about can be in the positive or negative with the same meaning:
"I warned them about not swimming in a bay full of sharks."
"I warned them about swimming in a bay full of sharks."
(not a teacher, just a language lover)