Definition - What does Sukha mean?
Sukha is a Sanskrit word which can be translated as “happiness,” “ease” or “bliss.” Its literal translation is often given as “good space,” coming from the Sanskrit words, su (good) and kha (space).
In the "Rig Veda" it has often been explained in contrast to preya (pleasure). This is because sukha is a deep and lasting state of happiness, while preya is a temporary state, or a passing pleasure.
Yogapedia explains Sukha
In terms of yoga practice, it is stated in Patanjali's Yoga Sutras 2.46, sthira sukha asanas, that an asana should be both sthira (stable) and sukha (comfortable). In other words, it is important that there exists an equal balance of striving to achieve and maintaining a pose as there is in the enjoyment and ease of holding the pose. If there is too much striving, then finding a sense of inner peace becomes difficult. Likewise, if there is too much ease, a pose may become passive and awareness drifts.
Many people who have practiced yoga and/or meditation have experienced a sense of meditative absorption (jhana) and describe this sensation of sukha as the feeling of bliss they have been looking for.