The synonym for "Brief" is determined by its definition: short in duration or extent, not time-consuming. Analyzing the provided options:
- Long: The antonym of "brief," indicating extended duration.
- Quick: Pertains to speed, not directly to duration.
- Short: Aligns with "brief" regarding duration or extent, thus it is a synonym.
- Slow: Relates to speed, not duration.
Consequently, "Short" is the synonym for "Brief."