Final answer:
The temperature at which a substance emits enough vapour to burn continuously is termed the fire point.
Step-by-step explanation:
The term that indicates the temperature at which a substance gives off enough vapour to burn continuously is known as the fire point. This is different from the flash point, which is the temperature at which a liquid gives off vapor in sufficient concentration to ignite in the air when exposed to a flame, but not continuously burn. The fire point is usually a few degrees higher than the flash point because it represents the temperature at which enough vapors are produced to support combustion continuously. Viscosity index and pour point are unrelated terms; viscosity index is a measure of a fluid's change in viscosity with temperature, and pour point is the lowest temperature at which a liquid flows.