What is a synonym for motive?

Here are some synonyms for motive, depending on the specific context:

General:

* Reason

* Cause

* Purpose

* Incentive

* Impetus

* Rationale

* Justification

* Intent

* Driving force

* Underlying factor

More specific:

* For a crime:

* Premeditation

* Gain

* Spite

* Vengeance

* For personal actions:

* Desire

* Ambition

* Goal

* Aspiration

* Need

Informal:

* Why

* What's in it for them?

The best synonym will depend on the specific situation and the nuance you want to convey.