There are five Yama's, and Ahimsa is the first and most paramount yama, and will almost always take precedence over the others. Ahimsa loosely translates as "to not bring harm to self or others, through thoughts or actions". At least this is my interpretation of it.
Did you know that "Yoga" is actually a system made up of eight limbs, and is not just the physical practice that we are led to believe what yoga is out west? There is more to yoga than flowing through movements and poses. The physical movements and poses are only one of the eight limbs, "Asana", pronounced Ahh-sah-nah.