Katie is a short form of the forename Catharine - Catherine - Katharine - Katherine. There are two main types of such shortenings: they are convenient for writing, e.g. in lists; or they are essentially spoken pet-names, and thus informal. (See Conventional abbreviations for forenames.)
|Short form||Long form||Informal or written||Other short forms||Remarks|
|Katie||Catharine - Catherine - Katharine - Katherine||informal||Cath(ie), Kath(y), Kate, Kitty|
- Note that any informal form may be spelled in different ways. Notably, any spelling listed that ends in '-ie' may be written with the ending '-y', and vice versa.