What is the difference between stupidity and ignorance?

Stupidity is when you are unintelligent, while with ignorance you may or may not be very smart but you just aren't very good at using your knowledge correctly.

Ignorance: when you simply don't know something, but you probably could learn it. A new person in train for example.

Stupidity: when you don't know something and probably can't learn it.

Ignorance is lack of knowledge.
Stupidity is lack of intelligence or common sense.
An intelligent person can be ignorant, and a stupid person can be knowledgeable.

stupidity means you have some knowledge but not a lot. Kinda like Dumb. But you can be Albert Einstein and not use your knowledge correctly or with any sense. that is being ignorant. :)