Is there a word for something with a constantly changing or not easily identifiable form?

Example: If a person sometimes acts shy but other times is more extroverted, so you’re not sure how to describe their personality — is there a word for that state of not really knowing what category a person or thing falls into?


Temperamental is what you're looking for.

A temperamental person is someone whose behaviour is unpredictable or whose mood changes suddenly.

Capricious and mercurial can also be used for such kind of person.

Mercurial: If you describe someone as mercurial, you mean that they frequently change their mind or mood without warning. [Collins Dictionary]

Capricious: having a tendency to sudden unpredictable changes of attitude or behaviour. [Collins Dictionary]

Due to their capricious and erratic behaviour, they are unclassifiable.

If a person sometimes acts shy but other times is more extroverted

Ambivert: a person whose personality has features typical of both introverts and extroverts.

  • 1
    Yes to all above (except perhaps "ambivert" for its oddness), but "mercurial" is the one that popped into my mind first.
    – RobJarvis
    Jul 6 '20 at 21:35

Some suggestions:

Ephemeral Lasting a very short time; short-lived; transitory.

Volatile Changeable; mercurial; flighty; fleeting; transient.

Elusive Eluding or failing to allow for or accommodate a clear perception or complete mental grasp; hard to express or define.


Inchoate may serve.

Strictly speaking it means imperfectly formed or not fully formed, but your audience may not quibble about that subtle difference.


'Enigmatic' could be the word you are looking for.

  • You should include the dictionary definition of the chosen word that makes it suitable in this case. Jul 5 '20 at 7:20
  • I think the choice is obvious for any native speaker. However, as for your curiosity, see sense 2 at dictionary.com/browse/enigma Jul 5 '20 at 9:15
  • If you edit that link and that definition into the answer, it will be a better answer.
    – Davo
    Jul 6 '20 at 16:06
  • Thanks for the suggestion. Jul 6 '20 at 18:46

The term chameleon-like (sometimes, see eg Merriam-Webster, without the hyphen, chameleonlike) is used of such people. Collins defines the metaphorical usage of the noun:

chameleon [noun] ...

  • (2) a changeable or fickle person

adjective: chameleon-like

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