These are the closest you can get to humans on this world with the only differences being their capacity to harness magic and a difference in height with the Pos being on average 154cm tall (5ft 2) as fully grown adults they also tend to be slimmer and more sinuously built.

Poskin (in the language of the Ki (Dwarfs))
Poselfa (in the language of the Sin (Elves))
Poienta (in the language of the Linta (Bird-Like Creatures))
Possfa (in the language of the Det (Reptillian Humanoids))
Pos (in the local langauges of most Pos):
(Variations:
Poska
Pes
Posla
Poseen)

They have a sinuous or wiry build with densely packed but not bulky musclature . It is hard for them to put on weight and on average they weigh far less than a human.
Otherwise they are built like an average human simply being far smaller and skinnier as well as stronger and more mobile.

White
Tanned
Brown
Black

154cm or 5ft 2" when fully grown - this applies for both sexes.

30kg when fully grown - this applies for both sexes.

They are the most human of the races with delicate features and softly pointed ears - but by far the or most notable feature is their tendency (around 97% have this) to have heterochromia (two different coloured eyes) the remaining 3% all have albinism (lack of pigment).

They can vary greatly with differences in height ranging from around 4ft 5" to 5ft 6" and a miriad of different skin tones, hair and eye colours along with a myriad of different body types (though they tend to lean on the skinny side of things with barely noticeable muscles).

Trousers, shirt and shoes generally patterned - but as they are the most wide spread and varied race there is no real average clothing with each region having there own unique traditional dress.

They are smart with a natural knack for maths, chemistry, alchemy and magic.

They are physically impressive being much stronger than your average human despite what their build might suggest - they are easily able to lift 2 times their body weight.

They are nimble and quick footed with an excellent sense of balance and a natural capacity for acrobatics.

Their eyes can pick up the broadest array of colours of all the races and their hearing is second only to the Ki (Dwarfs).

They naturally work well in groups with little to no squabbling or infighting.

Compared to the majority of the other races they are small and therefore weak.

They have poor stamina so have to rely on transport to get them over large distances.

Their night vision is poor, so much so that they are effectively rendered blind after dark.

Only certain members of the race have innate magic.

Compared to other races their sense of smell is terrible with only a handful of scents picked up.

They are the only race to be born with no natural weapons (ie. the Sin (Elves) have poisoned fingernails, the Ki (Dwarfs) have very sharp teeth that can rip through flesh, the Det (Reptillian Humanoids) have glands that secrete poison through their fangs, and the Linta (Bird - Like Creatures) have sharp talons and beaks.

The typical life span of a Pos is 100 - 110 years of age.

Too varied a race to talk in general terms - they are spread throughout the world speaking varied languages,and developing their own unique cultures