Do npc's learn?

Greetings

Strange question here but I was wondering if npc's in their current state actually learn like players can learn with skills.

I was at the red skeletons at the graveyard and my character could kill them easily but I went back again some time later and they were stronger.

Ok if this is due to good/ bad day then fine. But the question here is do npc's learn?

From what I remember, yes.
An old example would be the sheep, go in, attack them, heal them with a mage and so on and so forth.
They leveled in dodge and what-not if I'm not mistaken.

But on reds, perhaps a mage decided to pg Mes Pen one day, giving the beasts a heads up.

Hopes some of this is at least helpful

Or perhaps your char was having a good/bad day? (Condition message when you log on) If they were feeling stronger the first time, or feeling weak the second, it could affect their performance.

[Athian]

Technically an NPC can be trained, but they do not learn at any exceptionally advanced rate. One day of training an NPC might yield some experience, but unless someone took the monster away and trained it for days and days in a particular set of skills it probably would not become significantly stronger then it was before.

[Estralis Seborian]

The strength of monsters is randomised within certain boundaries each respawn. So, one day, you might encounter a tougher demon skeleton than the day before.

The other answers apply, too.

[pharse]

For technical correctness, one should mention that NPCs can't attack or be attacked, so they can't gain any fighting skill by fighting. You actually speak of monsters, as Estralis implicitly pointed out.

So no super sizing the sheep again?