1. a person who watches or notices something
2. a person who attends a meeting or event to watch but not participate
Usage: formal
3. a person who follows or obeys a rule, custom, or religious practice

Examples

• The bird observer spotted a rare species in the park.
• She was a keen observer of human behavior.
• UN observers monitored the election process.
• He attended the meeting as an observer, not a voting member.
• The scientist was a careful observer of the experiment.
• She is a strict observer of religious traditions.
• Casual observers might miss the subtle differences.