Several major changes are apparent in Diablo III; compared to Diablo II, each character class has many more skills available to use (Diablo II had only a maximum of '''thirty''' skills per character), while in a single skill tree in Diablo III can have in excess of '''eighteen'''. Also notable, is that Diablo III separates a skill tree into '''Tiers''' - some skills that exist on higher Tiers require the learning of a skill in a lower Tier; likewise, a higher Tier may require a certain number of skill points spent in a lower Tier to access any skills in it. So far, there appears to be a maximum of exactly '''six''' Tiers for any given skill tree (Tier I is level 1 to 4, Tier II begins at level 5, Tier III begins at level 10, Tier IV begins at level 15, Tier V begins at level 20, and Tier VI is level 25 and onwards).

So far, it is not known if each skill tree will have the same number of skills for each character class, as it were in Diablo II (each skill tree had exactly ten skills), but from inferring what has been revealed already, a single skill tree in Diablo III ''may'' have more than at least '''twenty''' skills. Take for instance, the [[Wizard]]'s [[Conjuring Skill Tree]] - it has '''ninteen''' skills, distributed over '''four''' Tiers. There are Since there appears to be (at least for now anyway) a maximum of '''six''' Tiers, the lack of skills in the final two Tiers have indicate that there are more yet to come. This is the same for the [[Wizard|Wizard's]] other skill trees, '''nineteen''' in the [[Arcane Skill Tree|Arcane]] & [[Storm Skill Tree]], across at least '''four''' Tiers, with the further two Tiers not yet implemented. Take note however, that as the game progresses in development, the current arrangement of skills may change (some may shift to be discloseda higher or lower Tier).

You can look further at the above known class [[skills]] (in the [[Diablo_3_Basics#Character_Classes|Character Classes section]] on this page) for detailed information about what has been revealed so far, but one big user interface (UI) change for character abilities is that skills are now accessed via a '''skill bar''', supplanting the functionality of the potion bar in Diablo II. It works similar to the skill bar in World of Warcraft (WoW), where more than two skills can be accessed without using the function hotkeys (F1, F2 etc). Read more about the [[potion]] changes below.