The principal two idiopathic forms of Diabetes mellitus are known as types 1 and 2. The term "type�1 diabetes" has universally replaced several former terms, including childhood-onset diabetes, juvenile diabetes, and insulin-dependent diabetes. Likewise, the term "type�2 diabetes" has replaced several former terms, including adult-onset diabetes, obesity-related diabetes, and non-insulin-dependent diabetes. Beyond these two types, there is no agreed-upon standard nomenclature. Various sources have defined "type 3 diabetes" as, among others, gestational diabetes, insulin-resistant type�1 diabetes (or "double diabetes"), type�2 diabetes which has progressed to require injected insulin, and latent autoimmune diabetes of adults. There is also maturity onset diabetes of the young which is a group of several single gene (monogenic) disorders with strong family histories that present as type�2 diabetes before 30 years of age.