I am trying to clarify this for Class 8 Science. Their textbook says "It is the lowest temperature at which a substance catches fire". However, it does not clarify whether it is on its own or due to an external source. I read through various websites and there are both kinds of definitions put up! Some also mentioned a flash point. So wanted to know what the proper definition of ignition temperature is and how it differs from flash point. Thanks!
Autoignition Temperature: the lowest temperature at which a substance spontaneously ignites without a source of ignition (such as a flame or spark).
Flash Point: the lowest temperature at which the vapours of a (volatile) material will ignite, with an ignition source.
Ignition temperature means the same thing as autoignition temperature according to Merriam Webster.