Onlooker (noun)

A person who watches or observes an event or activity, often without participating.

Origin:

Derived from the middle english word 'onlooker' meaning 'someone who looks on'.

Examples:

1. The onlookers crowded around the street performer, watching as he juggled knives.
2. The onlookers gasped in amazement as the firework display lit up the night sky.
3. The onlookers at the parade cheered as the marching band passed by.
4. The onlookers at the accident were horrified by what they saw.
5. The onlookers at the tennis match were impressed by the player's skill and grace.