Which word describes a substance that is very flammable?

The term "inflammable" is used to describe a substance that is very flammable, meaning it can easily ignite and catch fire. The prefix "in-" in this context can be misleading because it is often interpreted as negation, but in this case, it actually comes from the Latin "inflammabilis," which means "able to catch fire." Thus, inflammable substances can pose significant fire hazards due to their tendency to ignite with minimal heat or spark.

On the other hand, "combustible" also refers to substances that can catch fire, but it generally implies a broader range of materials that may require more heat to ignite compared to something specifically labeled as "inflammable." "Incombustible" describes materials that do not burn, thus demonstrating a complete lack of flammability. Lastly, "stable" refers to substances that do not change chemically under normal conditions, which does not inherently relate to flammability. Therefore, among the provided options, "inflammable" is the term that most accurately indicates a high level of flammability.