There is no special term for abbreviations whose pronunciation involves the combination of letter names with words or with word-like pronunciations of strings of letters, such as "JPEG" and "MS-DOS" . Similarly, there is not a unique name for those that are a mixture of syllabic abbreviations and initialisms; these are usually pronounced as words (e.g., "radar" from "radio detection and ranging", and "sonar" from "sound navigation ranging", both consisting of two syllabic abbreviations followed by a single acronymic letter for "ranging"); these would generally qualify as word acronyms among those who use that term. There is also some disagreement as to what to call an abbreviation that some speakers pronounce as letters but others pronounce as a word. For example, the terms "URL" and "IRA" (for "Individual retirement account") can be pronounced as individual letters: and , respectively; or as a single word: and , respectively. The same character string may be pronounced differently when the meaning is different; "IRA" is always sounded out as "I-R-A" when standing for "Irish Republican Army".