flaw; defect; malfunction; bug
Broadly used for physical defects, system errors, software bugs, and operational failures. Often appears in technical and business contexts.
There is a malfunction in this computer.
This software still has several bugs.
Production was halted because a malfunction occurred in the machine.
Describes a situation or condition that is inconvenient or not working as desired. Less common than the noun sense.
My current place is inconvenient because it's far from the station.
A bug occurred in the system.
The engineer fixed the bug.
The user reported the malfunction.
欠陥 implies an inherent structural flaw, whereas 不具合 can describe a temporary or operational malfunction as well.
バグ is the casual loanword specifically for a software error, while 不具合 is the more formal, general business/technical term.
不備 means something is incomplete or missing a required element, while 不具合 focuses on something not functioning properly.
Compound of 不 (fu, 'not') and 具合 (guai, 'condition, state'). Literally 'not in good condition'.