1
general::
Phrase(s): form an opinion
to think up or decide on an opinion. (Note the variations in the examples.) • I don’t know enough about the issue to form an opinion. • Don’t tell me how to think! I can form my own opinion. • I don’t form opinions without careful consideration.
McGrawhill's American Idioms And Phrasal Verbs
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Make up one's mind or decide what one thinks about something. For example, I need more facts before I can form an opinion about this issue, or Don't tell me your views; I want to form my own opinion.
American Heritage Idioms