Sorry Bob & Pradeep - I stand by my answer.....
One of the reasons I dislike the "ITIL Silver Bullet" (or to be fair any "Silver Bullet")........
I may be "shouting at the devil" or "pissing in the wind" but I ALWAYS contest using categorisations that are unclear.... ITIL isn't faultless!!!
I know ITIL uses Major and Significant (I also know that its unlikely they will change it for me :-( ) but the use of these terms is so obviously WRONG (not least because it causes so much confusion)......
Just search any ITIL discussion forum for examples..... "Nobody" knows the difference so they have to make their own (local) definitions......
The general consensus is that "Significant" is "BIGGER" than "Major"........
(Sometimes this means Major needs/gets "Local CAB" approval and Significant needs/gets "Global CAB" approval etc but that is also (correctly) down to local process definition)
If your description of a Change (or Incident, Project, Implementation etc etc) based on "Categorisation" is not clear then you have to make them clear. If the words are interchangable you MUST be using the WRONG words.....
Cat 1 - Minor or Trivial change that can be carried out during working hours with little or no impact
Cat 2 - <insert words of choice> change that will have impact on multiple users in a single location/impacts users of a single system.
Such changes need to be approved by local CAB and scheduled with user agreement or outside core hours.
Cat 3 - <insert words of choice> change that will impact multiple users in multiple locations/impacts multiple systems.
Such changes needs to be approved by local CAB and scheduled with user agreement or outside core hours.
List of words to choose for insertion: Major, Significant, Major & Significant, Major or Significant
If you (just) Used Cat 1, Cat 2 and Cat 3 it wouldn't be immediately obvious (except that by using numbers there is an impllied scale - you only need to work out which way it runs) - but the definitions would clarify.
If you (attempted) to use Minor, Major and Significant - Major and Significant are patently still confusing (until you read understand the wording round approval etc).
So Minor, Major & Significant are NOT CLEAR ENOUGH to use as categorisations because "Joe Bloggs off the street" cannot possibly understand them!!! So why on earth would you use something so fundamentally wrong!!!???
Some "ITIL implementations" add another category of "Urgent" (or Emergency etc) where as some (more correctly IMHO) model that "Urgent/Emergency" changes could still be Cat1, 2 or 3 AND Urgent/Emer.
Apologies for the rant but (as you might have gathered) it is a point I feel strongly about (one of many :-) ).