Ok here is what i think the 18 skyrim skills are.
I've marked oblivions 21 skills down to make it easier.
:OBLIVION SKILLS: COMBAT1: Block 2: Armourer 3: Heavy Armour 4: Blunt 5: Blade 6: Athletics 7: Hand to hand
MAGIC1: Destruction 2: Alteration 3: Illusion 4: Conjuration 5: Mysticism 6: Restoration 7: Alchemy
STEALTH1: Security 2: Sneak 3: Acrobatics 4: Light armour 5: Marksman 6: Mercantile 7: Speechcraft
Total skills = 21.:SKYRIM SKILLS:COMBAT1: Block 2: Smithing 3: Heavy Armour 4: One handed 5: Two handed 6: Hand to hand.MAGIC1: Destruction 2: Alteration 3: Illusion 4: Conjuration 5: Restoration 6: Enchanting.STEALTH1: Stealth/thievery 2: Light Armour 3: Acrobatics 4: Archery 5: Speechcraft 6: Alchemy.Total skills = 18.Ok ,i'll explain why i think the skyrim skills,are what they are:
COMBAT: I've left block the same,because it's what you do,be it with a shield ,single weapon,double handed weapon or duel wield.
I've left hand to hand ,because it's fun,they have worked on close quarters fighting ( more intense ) it's a combat art in it's own right,and i believe there would be enough perks for it.
I taken athletics away completely,because i think the PC may have a set speed ( maybe race dependant also ) while jogging,with the exception of weight carried.
We now have a sprint option,which to me suggest's athletics is gone,stamina and weight will now depend on that.
I also believe heavy armour will stay as it is in combat,for obvious reasons.
MAGIC: Ok this is simple,alchemy to stealth,mysticism gone ( moulded into other magics ),and of course we have enchant which = 6 skills,with the others.
STEALTH: Ok i strongly believe,that sneak and security have been joined as one skill.....why?...Because i believe in the world of TES security is a stealth skill,to me it goes hand in hand with sneak ( some won't agree ). If you looked at most of the preset classes in the other games,security was important to rogues,assassins,thieves etc.
Security was needed to break in houses etc to steal or murder.And naturally you would want to do that undetected,so i believe the two go hand in hand.
Plus i don't think there are too many perks for security alone...my view.
Light armour is still important for stealth types,they too have to fight toe to toe sometimes,so need light protection.
I have also kept acrobatics,it can be important to all classes,but vital to thieves,rogues,assassins etc. So they can be agile,leap further,jump on rocks,roll etc.I believe it's vital to that type.
So i believe that may stay....the only problem i have with this is maybe perks,but we'll see.
Now in the GI screens from a while back we saw a skills screen ,and to the far left on that screen was "aft",which is obviously "speechcraft.
I believe there is no need for mercentile,because speechcraft covers that anyway. If your good at talking and getting info ( be it charm.sly,or fear ) off people,you gunna do the same with bartering etc. Your a smooth talker,it makes sense.
Finally alchemy. Alchemy is not magic,it's science,and fits just as well with stealth ( in my view ) as magic,and it also enables a craft for ech type..Combat,magic,stealth,seems fair.
Anyway looking at oblivions skills ,thats what i have come up with and why.
You judge whatever you like about it