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.

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    Yes to all above (except perhaps "ambivert" for its oddness), but "mercurial" is the one that popped into my mind first. – RobJarvis Jul 6 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.

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Inchoate may serve.

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

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

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  • You should include the dictionary definition of the chosen word that makes it suitable in this case. – KillingTime Jul 5 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 – Cosmopolitan Jul 5 at 9:15
  • If you edit that link and that definition into the answer, it will be a better answer. – Davo Jul 6 at 16:06
  • Thanks for the suggestion. – Cosmopolitan Jul 6 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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