vested interest
Vested interest (noun) means a personal stake in how something turns out, which gives you a reason to argue for a particular outcome and may make your advice unreliable. Example: “He has a vested interest in the merger going ahead, so treat his figures carefully.”
How to use vested interest
Learner’s notesIn plain EnglishA reason to want things to go a certain way because you personally gain from it.
Neutral to slightly critical; common in journalism, politics and business.
The phrase is 'vested interest', not 'invested interest' — the latter is a common mishearing.
Trace the full origin ↓Fill the gap
Can you complete this real example?
He has a _____ in the merger going ahead, so treat his figures carefully.
Etymology
From vested, meaning legally settled or secured, from Latin vestire 'to clothe'.