Difference between sign up and sign in


Senior Member
Hello everyone!

Please advise whether there is any difference between sign up and sign in.
I've always thought that sign up means initially subscribe to a service, app, etc. and sign in is the same as log in.
Am I right?
And the antonyms will be sign off and sign out, won't they?

Thank you in advance.
  • Copyright

    Senior Member
    American English
    Here is a previous thread:
    sign in/up

    You can sign up for many things: a subscription, a group, a campaign, a service, military service, etc.
    The antonyms will vary depending on what you signed up for, but we wouldn't use sign off (which is often used by radio or television presenters to describe them ending their program). You would unsubscribe from a subscription, for example. You might just stop attending a real ground, or unfollow a Facebook group. You would get a discharge from the military, so your leaving would generally be out of your control.

    You sign in to record your arrival someplace.
    When you leave, you sign out.
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