underlying problem
noun phraseUK /ˌʌn.dəˈlaɪ.ɪŋ ˈprɒb.ləm/
US /ˌʌn.dɚˈlaɪ.ɪŋ ˈprɑː.bləm/
The real problem that is hidden under the one you can see.
The doctor found the underlying problem that was making her sick.
OTHER MEANINGS
2. A basic fault in a system that causes many smaller troubles.
The underlying problem in the old school was that the roof leaked.
3. The main reason behind a person's bad behavior.
The teacher looked for the underlying problem instead of just punishing him.
4. A deep issue that is hard to see at first.
They fixed the flat tire, but the underlying problem was a sharp nail on the road.