Is there a word for making an assumption of something larger from a small external part (possibly erroneously)?

For example:

judging a person's entire moral character by one of his crimes.

  • Hi @Eliana, Have you researched this at all yourself? If so, please add that information, including citations. Ideally, questions on English Language & Usage will reflect some research effort by the requester. Thanks!
    – freeling10
    Commented Feb 3, 2017 at 3:03

4 Answers 4



When you extrapolate, you use specific details to make a general conclusion. For example, if you travel to Canada and encounter only friendly, kind natives, you might extrapolate that all Canadians are friendly.


  • I think generalize (a synonym listed on the page you linked to) would work better than extrapolate.
    – J.R.
    Commented Feb 3, 2017 at 2:37
  • @J.R. - For mathematicians, and people who work with math, extrapolate is a strong, specific word. It is more prone to error than generalize. Commented Feb 3, 2017 at 2:40
  • Yes, exactly. (I usually associate that word with data and experiments, not, say, judging a person's moral character.) That said, the Wordnik page has some examples that fit quite nicely. Interesting.
    – J.R.
    Commented Feb 3, 2017 at 2:43

As for the part about "possibly erroneously," there's the term hasty generalization. From Wikipedia:

Hasty generalization is an informal fallacy of faulty generalization by reaching an inductive generalization based on insufficient evidence—essentially making a hasty conclusion without considering all of the variables.

There's also the idiom jumping to conclusions.


This is called judging a book by its cover: judging the whole by some prominently visible part of the whole.

See Don't judge a book by its cover (Wikipedia).


It is some times called judging (yes, the same word as used in your example!).


judge verb
judged; judging

5 : to form an estimate or evaluation of : trying to judge the amount of time required;
especially : to form a negative opinion about : shouldn't judge him because of his accent

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