Here's why:

* Flash Point: The key difference lies in their flash points. Flammable liquids have a flash point below 100°F (37.8°C), meaning they can ignite with a spark or flame at relatively low temperatures. Combustibles have a flash point above 100°F (37.8°C).

* Ignition Temperature: While flash point refers to the temperature at which a liquid produces enough vapor to ignite, the ignition temperature is the minimum temperature required for sustained combustion. Flammable liquids typically have lower ignition temperatures than combustibles, making them more likely to catch fire.

In essence:

* Flammable liquids: Ignite easily under normal conditions and present a significant fire hazard.

* Combustible liquids: Require higher temperatures to ignite and are generally considered less hazardous.

Important Note: Both flammable and combustible liquids pose fire hazards. Always handle them with caution and follow safety guidelines.