on one’s side—
1. said of smth. giving a person an advantage and increasing his chances of success:
- He has youth on his side, and it is odds but he gets over it [disease].
2. said of smb. supporting a person in an argument, etc.:
- The polluters often have a strong commercial lobby on their side, while the antipolluters must rely on voluntary effort.
on the side—
1. said of work done in addition to one’s regular occupation:
- Norm decided to start looking at his hobby as a means of making a little money on the side.
2. said of smth. done secretly or illicitly:
- If I married him, I’d need a boy friend on the side to keep me entertained. Not for sex, for conversation.
Note: The expression does not correlate in meaning with the phrase on the sidelines—used of smb. not participating in an activity, being merely a spectator:
- For most of this debate, I have sat on the sidelines, watching and listening with interest.