Which one is right?

1 I'm free Thursday.
2 I'm free on Thursday.

I thought if you want to say that something happens during a particular day, you should use on, as in 'They’ll be here on Tuesday.' But I came across the title sentence without on, and now I don't know exactly when to use on before a specific day and when not to!

  • If someone is asking you to help them move, the correct phrasing is, "I'm BUSY on Thursday". :-)
    – Jay
    Dec 8, 2015 at 21:44
  • Or: "I'm busy Thursday."
    – user20792
    Dec 8, 2015 at 21:51

1 Answer 1


Actually, even for the example that you gave, "on" really isn't necessary:

You could have either

They’ll be here on Tuesday.


They'll be here Tuesday.

Same goes for "free on Thursday" vs "free Thursday." In my experience, both are used more or less interchangeably.

  • 1
    So when is it necessary to use on ?
    – Færd
    Dec 8, 2015 at 19:35
  • @MJF That is actually a complicated question in my mind. For example, if you're talking about an event, "The game will be on Friday" sounds MUCH better than, "The game will be Friday." You may need to wait for someone else to expand on general rules for "on," because I can't seem to come up with a general rule.
    – Alex K
    Dec 8, 2015 at 19:38
  • 3
    I've been thinking about this for a little while and I can't come up with a construction that seems to require the "on". It is definitely preferred in some cases (as in Alex's comment), but not required in any situation I can think of right now. Dec 8, 2015 at 19:41
  • Well, hearing that from native speakers is a relief. Thanks.
    – Færd
    Dec 8, 2015 at 19:44
  • Umm, for some reason, the versions without on sound very strange to me. Dec 8, 2015 at 20:00

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