The main difference between "start" and "start over" is that **"start"** refers to beginning something for the first time or initiating an action, while **"start over"** means to begin again from the beginning, often after stopping or failing.

### Examples:

- **Start**: "I will start my homework now." (beginning for the first time)

- **Start over**: "I made too many mistakes, so I need to start over." (begin again from scratch)

In short, "start" is the initial beginning, and "start over" is a fresh start after something has already been started.