Everywhere I have read that the correct preposition is on for weekdays.
Would it still be OK to say: "Monday is the hardest in weekdays"?
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Sign up to join this communityEverywhere I have read that the correct preposition is on for weekdays.
Would it still be OK to say: "Monday is the hardest in weekdays"?
Your sentence makes no sense.
I assume you mean:
Monday is the hardest weekday
That would mean you are very busy on Monday and it is the hardest day that is a weekday.
You could also say
Monday is the hardest of the weekdays.
or even
Monday is the hardest of weekdays.