Back formation refers to an usually abnormal type of word formation where a shorter word is derived by deleting an imagined affix from a longer form already in the language. Take “televise” for example. The word “television” appeared before “televise”. The first part of the word “television” was pulled out and analyzed as a root, even though no such root occurs elsewhere in the English language. Instead of taking out part of a word as a root, back formation allows us to take out a word of a given category and form a new homophonous word of a different category, such as the noun form “white-wash” that becomes the verb form “whitewash”.