a fundamental flaw — basic defect
collocationC1IELTS 7+neutraloccasional
a very basic or central weakness or problem in something, especially one that affects its whole structure or purpose.
Say it like a native
Textbook The plan possesses a fundamental flaw in its underlying design.
Native There's a fundamental flaw in the plan.
'Possesses a flaw' for an abstract thing sounds bookish; natives say 'there's a flaw in'.
Pattern: a fundamental flaw (in something)
In use
- There is a fundamental flaw in the way the new system processes data.study
- In my opinion, the proposal has a fundamental flaw because it doesn't consider the needs of people living in rural areas.IELTS speaking
Common mistake
✗ The argument has a fundamental flaw on it.
✓ The argument has a fundamental flaw in it.
'A flaw IN something', not 'on'.
Common collocations
a fundamental flaw in— the argument, the design, the logic, the system
Don't confuse it
Unlike 'a minor flaw' or 'a small flaw', which refer to less important problems, 'a fundamental flaw' means the problem is so basic that it undermines the whole thing.