Ignorance is a lack of knowledge. The word ignorant is an adjective describing a person in the state of being unaware, and is often (incorrectly) used to describe individuals who deliberately ignore or disregard important information or facts.
Ignoramus is commonly used in the United States as a term for someone who is willfully ignorant. Ignorance is distinguished from stupidity, although both can lead to "unwise" acts.
The writer, Thomas Pynchon, articulated the following about the scope and structure of one's ignorance: "Ignorance is not just a blank space on a person's mental map. It has contours and coherence, and for all I know rules of operation as well. So as a corollary to [the advice of] writing about what we know, maybe we should add getting familiar with our ignorance, and the possibilities therein for writing a good story."
The legal principle that ignorantia juris non excusat, literally "ignorance of the law is no excuse", stands for the proposition that the law applies also to those who are unaware of it.