act weird/weirdly: behave weird / weirdly [adjective vs adverb]


Senior Member
Hi everyone

I'm a little confused. Should we use adjectives or adverbs after behave/act?
Which one is more idiomatic?
To act so weird
To act weirdly

To behave impolite
To behave impolitely

I would be glad if you could give me your opinion. Thank you.
  • Juhasz

    Senior Member
    English - United States
    To act, when it means to behave (rather than to perform in a play) works like to be, to appear, etc. taking an adjective. If a person acts weird, they act in a manner that is weird. If a person acts weirdly, they read their lines in a strange manner.

    Despite having the same meaning, to behave does not work the same way. It takes adverbs, as most verbs do. That said, it seems to be more and more common for English speakers (at least Americans) to never use adverbs and only ever use adjectives. You might hear a native speaker say, "behave impolite."


    Member Emeritus
    English - US
    I agree with Benny (post #4). "Act weird" or "act crazy" is common, but I can't imagine anyone saying "behave impolite".
    But Juhasz doesn't give a location; perhaps it's common in a local dialect.
    Behave + adjective does exist--in support of Juhasz. Here are a couple results:

    A Christian's Divorce Time-Line!

    I want you to behave good and keep up the good work in school. I think if I were over there I would be so glad too.


    3 | The good one (Draco Malfoy love story) - Story | Quotev

    I want you to behave good and not like bibbling bummling band of baboons!!!"


    h2g2 - This is a Journal entry by Hati

    Jun 25, 2002 - Nevermind, I'm not sure I want you to behave decent anyway, wouldn't be the right thing for a party like RF! smiley - winkeye.



    Member Emeritus
    English - US
    The writings on those unedited sites don't make "behave good" or "behave decent" correct. They should be behave well and behave decently.


    Senior Member
    British English (Sussex)
    I'd say "He acts weird" is something of a set phrase by now, and certainly more idiomatic in casual speech then "He acts weirdly."

    Benny's examples sound very "folksy" or even uneducated to me, and I haven't come across that kind of thing much in BE. I wouldn't recommend using them in an effort to make your English sound "idiomatic". If in doubt, always use the adverb.
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