Revealing Paws

1. The region of a forelimb between shoulder and elbow (containing the humerus bone) of a biped; it does not include the forearm (the region between elbow and wrist). This is known colloquially as the upper arm. 

[Anatomical usage]

2.  The region between the shoulder and wrist of a forelimb if not used for weight-bearing or locomotion.  

All four limbs of cats and dogs are used for weight-bearing and locomotion, and so they are usually termed legs, not arms.

[Common usage]