A skill to which characters of a particular class have easier access than characters of other classes. Characters may buy class skills at a rate of 1 rank per skill point, as opposed to 1/2 rank per skill point for cross-class skills. The maximum rank for a class skill is 3 + character level.
With regards to creatures in general, a class skill is any skill in which a monster has acquired at least one rank or in which the creature has a racial bonus. Some monsters, such as the true dragons, have their class skills explicitly listed. Other monsters' class skills can be determined from their statistics blocks.
Creatures with a Swim speed always have Swim as a class skill. Creatures with a Climb speed always have Climb as a class skill. Skills listed in an entry merely because of synergy with another skill are not class skills. For example, a ssvaklor's class skills are Bluff, Listen, Sense Motive, Spot, Survival and Swim. It has other skill modifiers, such as Diplomacy, Disguise and Intimidate, that are due to synergy benefits granted by other skills. The statistics block also includes a Jump modifier due to its speed, even though Jump is not a class skill for the creature.