In recent decades the Yoga Sutra has become quite popular worldwide for the precepts regarding practice of Raja Yoga and its philosophical basis. "Yoga" in traditional Hinduism involves inner contemplation, a rigorous system of meditation practice, ethics, metaphysics, and devotion to the one common soul, God, or Brahman. At the same time, his Mahābhāṣya, which first foregrounded the notion of meaning as referring to categorization, remains an important treatise in Sanskrit linguistic philosophy.
In addition to the Mahābhāṣya and Yoga Sutras, the 11th c. text on Charaka by ChakrapAni, and the 16th c. text Patanjalicharita ascribes to Patanjali a medical text called the CarakapratisaMskritah (now lost) which is apparently a revision (pratisaMskritaH) of the medical treatise by Charaka. Some have cited the Patanjali reference in Yoga Sutra as possibly being from this text. Were he to be the author of all three works, it would be quite amazing, although such diversity would not be very uncommon in many early civilizations, as in the work of Pingala or Katyayana, both grammaticians who also worked in mathematics, or their contemporary Aristotle, say. At the same time, it is possible that the Patanjali hagiography extolled his persona considerably.
Even his name has been glorified; it is said that desiring to teach yoga to the world, he fell (pat-) from heaven into the open palms (-añjali) of a woman, hence the name Patañjali. He is also often respectfully referred to as Patanjali Maharishi, or great sage.
In one popular legend, Patanjali was born to Atri (First of the Saptha Rishis) and his wife Anusuya (this would make him go back to the time of the creation by Brahma). According to this tradition, Anasuya had to go through a stern test of her chastity when the Trimurti (Brahma, Vishnu, Siva) themselves came as Bhikshuks and asked her for Bhiksha. She passed their test by accepting them as her children and fed them while naked. She got the boon where all the 3 Murtis will be born to them. They were SomaSkandan or Patanjali, Dattatreya, and Durvasa.
Regarding his early years, a Tamil Shaivite tradition from around 10th c. AD holds that Patanjali learned Yoga along with seven other disciples from the great Yogic Guru Nandhi Deva, as stated in Tirumular's Tirumandiram (Tantra 1).
Nandhi arulPetra Nadharai Naadinom
Nandhigal Nalvar Siva Yoga MaaMuni
Mandru thozhuda Patanjali Vyakramar
Endrivar Ennodu(Thirumoolar) Enmarumaame
By receiving Nandhi's grace we sought the feet of the Lord
The Four Nandhis (Sanagar, Santhanar, Sanath Sujatar, Sanath Kumarar),
Siva Yoga Maamuni, Patanjali, Vyakramapadar and I (Thirumoolar)
We were thus eight disciples.
The ancient Kali Kautuvam also describes how Patanjali and Vyagrapada gathered along with the gods in Thillai near Chidambaram to watch Shiva and Kali dance and perform the 108 mystic Karanas, which formed the foundation for the system of Natya Yoga.
This Tamil tradition also gives his birth place in South Kailash, possibly the modern day Thirumoorthy hills near Coimbatore. Some other traditions feel that his being born in Bharatavarsha - the part of the ancient world corresponding to South Asia - is beneath his godlike status, and that he must have been born in the Jambudvipa, the mythical center of the universe.
It was my Grandfather who said, "Climb and see."
But it was Kalangi Nathar who gave me birth.
Patanjali,Viyagiramar,and Sivayogi Muni all so rightly said,
"Look! This is the path!" - Bhogar, 7000 sayings
This tradition also holds that Patanjali was a master of dance.
In contrast to the focus on the mind in the Yoga sutras, later traditions of Yoga such as the Hatha yoga focus on more complex asanas or body postures.
Patañjali defended in his yoga-treatise several ideas that are not mainstream of either Sankhya or Yoga. He, according to the Iyengar adept, biographer and scholar Kofi Busia, acknowledges the ego not as a separate entity. The subtle body linga sarira he would not regard as permanent and he would deny it a direct control over external matters. This is not in accord with classical Sankhya and Yoga.
Although much of the aphorisms in the Yoga Sutra possibly pre-dates Patanjali, it is clear that much is original and it is more than a mere compilation. The clarity and unity he brought to divergent views prevalent till then has inspired a long line of teachers and practitioners up to the present day in which his most renowned defender is B.K.S. Iyengar. With some translators he seems to be a dry and technical propounder of the philosophy, but with others he is an empathic and humorous witty friend and spiritual guide.The ("great commentary") of Patañjali on the of is a major early exposition on Panini, along with the somewhat earlier Varttika by Katyayana. Here he raises the issue of whether meaning ascribes to a specific instance or to a category:
Another aspect dealt with by Patanjali relates to how words and meanings are associated - Patanjali claims shabdapramâNaH - that the evidentiary value of words is inherent in them, and not derived externally - the word-meaning association is natural. The argument he gives is that people do not make an effort to manufacture words. When we need a pot, we ask the potter to make a pot for us. The same is not true of words - we do not usually approach grammarians and ask them to manufacture words for our use.  This is similar to the argument in the early part of Plato's Cratylus, where morphemes are described as natural, e.g. the sound 'l' is associated with softness.
Patañjali's writings also elaborate some principles of morphology (prakriyā). In the context of elaborating on Panini's aphorisms, he also discusses Kātyāyana's commentary, which are also aphoristic and sūtra-like; in the later tradition, these were transmitted as embedded in Patañjali's discussion. In general, he defends many positions of Panini which were interpreted somewhat differently in Katyayana.
Unlike Panini's objectives in the Ashtyadhyayi which is to distinguish correct forms and meanings from incorrect ones (shabdAunushAsana), Patanjali's objectives are more metaphysical. These include the correct recitations of the scriptures (Agama), maintaining the purity of texts (rakShA), clarifying ambiguity (asaMdeha), and also the pedagogic goal of providing an easier learning mechanism (laghu). This stronger metaphysical bent has also been indicated by some as one of the unifying themes between the Yoga Sutras and the Mahābhāṣya.
The text of the had diversified somewhat in the late Sanskritic tradition, and the nineteenth-century orientalist Franz Kielhorn produced the first critical edition and developed philological criteria for distinguishing Kātyāyana's "voice" from Patañjali's. Subsequently a number of other texts have come out, the 1968 text by S.D. Joshi and J.H.F. Roodbergen often being considered definitive.
Patanjali also writes with a light touch. For example, his comment on the conflicts between the orthodox Brahminic (Astika) groups, versus the heterodox, nAstika groups (Buddhism, Jainism, and atheists) seems relevant for religious conflict even today: the hostility between these groups was like that between a mongoose and a snake. He also sheds light on contemporary events, commenting on the recent Greek incursion, and also on several tribes that lived in the Northwest regions of the subcontinent.