The terms “word retrieval problem” or “word finding difficulty” imply that the person knows and understands the word, and has used it correctly before. However, they have difficulty retrieving such known words at times. Children and adults with language disorders are frequently found to have word retrieval difficulties. Often when a person (child or adult) is having difficulty retrieving a word they will have the sense that it is “on the tip of their tongue”: a state of affairs familiar to all of us; at other times they seem simply to “go blank”. They appear not to know answers when in reality they know, but are unable to express their knowledge.