There are many translations and commentaries on the Yoga Sutras. The character of each can perhaps be seen by the translation of the one sentence that gets repeated and quoted each time anybody talks about the book: Patanjali’s definition of Yoga.
Yoga is establishing the mind (chitta) in stillness. (Ravi Ravindra, The Wisdom of Patanjali’s Yoga Sutras: A New Translation and Guide, p. 5)
Yoga is the inhibition of the modifications of the mind (I.K. Taimni, Yoga Sutras by Patanjali, Science of Yoga, p. 6)
When you are in a state of yoga, all misconceptions (vrittis) that can exist in the mutable aspect of human beings (chitta) disappear. (Ashtanga yoga site)
Union is restraining the thought-streams natural to the mind. (The Yoga Sutras of Patanjali, The Threads of Union, Translation by BonGiovanni)
Union, spiritual consciousness, is gained through control of the versatile psychic nature. (The Yoga Sutras of Patanjali, by Charles Johnston)
Concentration, or Yoga, is the hindering of the modifications of the thinking principle. (The Yoga Aphorisms of Patanjali interpreted by William Q. Judge)