flaw
n. countablen. a small mistake, mark, or weakness that stops something from being perfect. It can be a crack in a cup or a problem in someone's plan.
n. a mark, fault, or imperfection that mars an object or character; a defect in a physical structure or a logical argument.
The diamond is cheaper because it has a tiny flaw.
The lawyer found a major flaw in the contract that allowed his client to leave the deal.
Despite the architect's brilliant vision, a structural flaw in the foundation eventually led to the building's condemnation just a decade after its completion.
From Middle English flawe, flay (“a flake of fire or snow, spark, splinter”), probably from Old Norse flaga (“a flag or slab of stone, flake”), from Proto-Germanic flagō (“a layer of soil”), from Proto-Indo-European plok- (“broad, flat”). Cognate with Icelandic flaga (“flake”), Swedish flaga (“flake, scale”), Danish flage (“flake”), Middle Low German vlage (“a layer of soil”), Old English flōh (“a fragment, piece”).
From Middle English flaugh, from Middle Dutch vlāghe or Middle Low German vlāge, ultimately from Proto-West Germanic flagā. Or, possibly of North Germanic origin, from Swedish flaga (“gust of wind”), from Old Norse flaga; all from Proto-Germanic *flagǭ (“blow, strike”). See modern Dutch vlaag (“gust of wind”).
Often used with the preposition 'in' to indicate where the defect is located.