CamelCase (or camel case), also known as medial capitals or Pascal case, is a term which refers to the practice of writing compound words having one or more internal uppercase letters. Such words may be formed, for instance, from phrases in which the elements are joined without spaces with each element having a capital letter within the compound. Pascal case words always start with a capital letter, but camel case allows the first letter to be either upper or lower case, as in "LaBelle", "BackColor", or "iPod". The name comes from the uppercase "humps" in the middle of the compound word, suggestive of the humps of a camel. The practice is known by many other names, the most common of which is Pascal case for upper camel case.
An early systematic use of medial capitals is the standard notation for chemical formulae, such as NaCl, that has been widely used since the 19th century. In the 1970s, medial capitals became an alternative (and often standard) identifier naming convention for several programming languages. Since the 1980s, following the popularization of computer technology, it has become fashionable in marketing for names of products and companies, and for 1990s online video games where players use pseudonyms (when spaces were not allowed). However, medial capitals are rarely used in formal written English and most style guides recommend against their use.