Other forms: ignorances
If you didn't do any of the reading or homework for your Russian history class, you are probably hoping the teacher won't call on you, so you can hide your ignorance, or lack of knowledge.
The noun ignorance is not a synonym for "stupidity," since its meaning is closer to "being uninformed" than "being unintelligent." Ignorance implies that a person or group needs to be educated on a particular subject. You might have heard the phrase "ignorance is bliss," which means that sometimes it's easier when you don't know the whole truth about something and can be blissfully happy, unaware of unpleasant realities.