Since the release of Mac OS X in 2001, Apple has continued to tweak and enhance its modern Mac operating system with regular refreshes. The OS itself remains nimble and useful, but the naming convention is starting to get long in the tooth.
After 15 years of revisions, OS X is on version 10.11, also known as El Capitan - but it could be the last version to sport that sort of version number. Mounting clues suggest that Apple will rename its Mac operating system as "MacOS," perhaps with the new version due this year.
The latest clue comes from Apple itself, thanks to a newly refreshed page on environmental responsibility. The page specifically mentions "MacOS" when talking about the average amount of use of a Mac computer, and it's listed alongside Apple's other operating systems (see below).
While "MacOS" has been used unofficially as shorthand for the operating system, Apple doesn't use the term officially for any purposes - but that could change. Last month, a "MacOS" reference was found in an Interface Builder document in OS X 10.11.4's System folder, which has helped fuel speculation on the matter.
Apple's annual Worldwide Developers Conference (WWDC) takes place in June, and if a naming change is coming, it should be announced then. Siri is rumoured to be added to the Mac operating system with this autumn's revision, so a change that significant could be a nice complement to a branding change.
Also, it's unclear for now whether Apple will stick to the lowercase formatting of its other operating systems: iOS, watchOS, and tvOS. Mac is a much more entrenched brand than the others, plus keeping the capitalisation would be a nice tribute to the classic Mac OS that preceded OS X. Whatever the answer, we should find out come June.