Overestimate (verb)
To judge too highly.
“I overestimated the number of attendees, and bought far too much food for the party.”
Overestimate (noun)
An estimate that is too high.
Underestimate (verb)
To perceive (someone or something) as having a lower value, quantity, worth, etc., than what he/she/it actually has.
Underestimate (noun)
An estimate that is too low.
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