[U] ~ (of / about sth) a lack of knowledge or information about sth:
widespread ignorance of / about the disease * They fought a long battle against prejudice and ignorance. * She was kept in ignorance of her husband's activities. * Children often behave badly out of / through ignorance. * I hate to admit my ignorance, but how does it work?
IDIOMS
ignorance is bliss (saying) if you do not know about sth, you cannot worry about it:
Some doctors believe ignorance is bliss and don't give their patients all the facts.
