Literally, a rein, curb or bridle, a moral rule or duty. Alternatively, a path, a way, a movement.
Niyama (Niyamah, Niyamana) is sometimes known as a minor or secondary observance (to Yama), meaning taming, subduing: a precept, restriction, rule.
Vajrasati prefers to interpret the Yamas as a rein or curb, as it implies steering rather than opposing strong forces or energies; and for Niyama taming as it again implies harnessing raw energy rather than getting rid of it as well as a precept as something by which to commit to. The Yamas consist in Satya (honesty), Ahimsa (the negation or voidness of hatred or violence), Asteya (not taking what is not given), Brahmacharya (literally in the shade of Brahma; meaning the refinement of mental/emotional energy through abstension from sex). And Aparigraha (non-covetousness, non-acquisition, freedom from desire).
The Asanas-the postures, positions assumed in the practice of some aspects of yoga.