English Reference
noun

defect

n.
US /ˈdifɛkt/ de·fect UK spelling defected, defecting, defects

  1. 01 B2 Upper Intermediate

    a physical problem or mistake in how something was made that stops it from working perfectly.

    a physical or functional imperfection, flaw, or blemish in a product or system.

    Simple

    The car was recalled because of a serious defect in the braking system.

    In context

    Quality control identified a structural defect in the wing assembly, forcing the manufacturer to halt production until the design could be rectified.

  2. 02 C1 Advanced Technical Math

    the amount by which something is less than what is needed.

    the amount or quantity by which something falls short of a required standard or total.

    Simple

    The accountant noted a small defect in the final budget totals.

    In context

    In geometry, the angular defect of a vertex describes the difference between the sum of the angles and the expected planar total.

A paediatrician working there today says she has seen an unusual amount of birth defects, including children born without eyes or with their intestines on the outside of their bodies.

The Guardian· 17 Aug 2026

If politicians who defect retain their seats, it would suggest that political structures can travel with them.

Al Jazeera· 14 Aug 2026

Borrowed from Latin defectus (“a failure, lack”), from deficere (“to fail, lack, literally 'undo'”), from past participle defectus, from de- (“of, from”) + facere (“to do”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level C1 · Advanced
Frequency Frequent
Updated