According to Monier Monier-Williams, the word "Patañjali" is a compound name from "patta" (Sanskrit: पत, "falling, flying") and "añj" (अञ्ज्, "honor, celebrate, beautiful") or "añjali" (अञ्जलि, "reverence, joining palms of the hand").
Louis Renou was among the many scholars who have suggested that the Patañjali who wrote on Yoga was a different person than the Patanjali who wrote a commentary on Panini's grammar. In 1914, James Wood proposed that they were the same person. In 1922, Surendranath Dasgupta presented a series of arguments to tentatively propose that the famed Grammar text and the Yoga text author may be identical.
The view that these were likely two different authors is generally accepted, but some Western scholars consider them as same.
Some in the Indian tradition have held that one Patañjali wrote treatises on grammar, medicine and yoga. This has been memorialised in a verse by Bhoja at the start of his commentary on the Yogasutras called Rājamārttanda (11th century), and the following verse found in Shivarama's 18th-century text:
योगेन चित्तस्य पदेन वाचां मलं शरीरस्य च वैद्यकेन। योपाकरोत्तं प्रवरं मुनीनां पतञ्जलिं प्राञ्जलिरानतोस्मि॥
English translation: I bow with my hands together to the eminent sage Patañjali, who removed the impurities of the mind through yoga, of speech through grammar, and of the body through medicine.
This tradition is discussed by Meulenbeld who traces this "relatively late" idea back to Bhoja (11th century), who was perhaps influenced by a verse by Bhartṛhari (ca. 5th century) that speaks of an expert in yoga, medicine and grammar who, however, is not named. No known Sanskrit text prior to the 10th century states that the one and the same Patanjali was behind all the three treatises.
In the grammatical tradition, Patañjali is believed to have lived in the second century BCE. He wrote a Mahabhasya on Panini's sutras, in a form that quoted the commentary of Kātyāyana's vārttikas. This is a major influential work on Sanskrit grammar and linguistics. The dating of Patanjali and his Mahabhasya is established by a combination of evidence, those from the Maurya Empire period, the historical events mentioned in the examples he used to explain his ideas, the chronology of ancient classical Sanskrit texts that respect his teachings, and the mention of his text or his name in ancient Indian literature. Of the three ancient grammarians, the chronological dating of Patanjali to mid 2nd century BCE is considered as "reasonably accurate" by mainstream scholarship.
The text influenced Buddhist grammatical literature, as well as memoirs of travellers to India. For example, the Chinese pilgrim I-tsing mentions that the Mahabhasya is studied in India and advanced scholars learn it in three years.
In the Yoga tradition, Patañjali is a revered name. This Patañjali's oeuvre comprises the sutras about Yoga (Yogasūtra) and the commentary integral to the sutras, called the Bhāṣya. Some consider the sutras and the Bhaṣya to have had different authors, the commentary being ascribed to "an editor" (Skt. "vyāsa"). According to Phillipp Maas, the same person named Patanjali composed the sutras and the Bhāṣya commentary.
Radhakrishnan and Moore attribute the text to the grammarian Patañjali, dating it as 2nd century BCE, during the Maurya Empire (322–185 BCE). Maas estimates Patañjali's Yogasutra's date to be about 400 CE, based on tracing the commentaries on it published in the first millennium CE. Edwin Bryant, on the other hand, surveys the major commentators in his translation of the Yoga Sūtras. He states that "most scholars date the text shortly after the turn of the Common Era (circa first to second century), but that it has been placed as early as several centuries before that." Bryant concludes that "A number of scholars have dated the Yoga Sūtras as late as the fourth or fifth century C.E., but these arguments have all been challenged", and late chronology for this Patanjali and his text are problematic.
Regarding his early years, a Tamil Saiva Siddhanta tradition from around 10th century AD holds that Patañjali 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 Patañjali Vyakramar
Endrivar Ennodu (Thirumoolar) Enmarumaame
We sought the feet of the Lord who graced Nandikesvara
The Four Nandhis,
Sivayoga Muni, Patañjali, Vyaghrapada and I (Thirumoolar)
We were these eight.
Whether the two works, the Yoga Sutras and the Mahābhāṣya, are by the same author has been the subject of considerable debate. The authorship of the two is first attributed to the same person in Bhojadeva's Rajamartanda, a relatively late (10th century) commentary on the Yoga Sutras, as well as several subsequent texts. As for the texts themselves, the Yoga Sutra iii.44 cites a sutra as that from Patanjali by name, but this line itself is not from the Mahābhāṣya. This 10th-century legend of single-authorship is doubtful. The literary styles and contents of the Yogasūtras and the Mahābhāṣya are entirely different, and the only work on medicine attributed to Patañjali is lost. Sources of doubt include the lack of cross-references between the texts, and no mutual awareness of each other, unlike other cases of multiple works by (later) Sanskrit authors. Also, some elements in the Yoga Sutras may date from as late as the 4th century AD, but such changes may be due to divergent authorship, or due to later additions which are not atypical in the oral tradition. Most scholars refer to both works as "by Patanjali", without meaning that they are by the same author.
In addition to the Mahābhāṣya and Yoga Sūtras, the 11th-century commentary on Charaka by the Bengali scholar Cakrapāṇidatta, and the 16th-century text Patanjalicarita ascribes to Patañjali a medical text called the Carakapratisaṃskṛtaḥ (now lost) which is apparently a revision (pratisaṃskṛtaḥ) of the medical treatise by Caraka. While there is a short treatise on yoga in the medical work called the Carakasaṃhitā (by Caraka), towards the end of the chapter called śārīrasthāna, it is notable for not bearing much resemblance to the Yoga Sūtras, and in fact presents a form of eightfold yoga that is completely different from that laid out by Patañjali in the Yoga Sūtras and the commentary Yogasūtrabhāṣya.
The Yoga Sūtras of Patañjali are 196 Indian sutras (aphorisms) on Yoga. It was the most translated ancient Indian text in the medieval era, having been translated into about forty Indian languages and two non-Indian languages: Old Javanese and Arabic. The text fell into obscurity for nearly 700 years from the 12th to 19th century, and made a comeback in late 19th century due to the efforts of Swami Vivekananda and others. It gained prominence again as a comeback classic in the 20th century.
Before the 20th century, history indicates the Indian yoga scene was dominated by other Yoga texts such as the Bhagavad Gita, Yoga Vasistha and Yoga Yajnavalkya. Scholars consider the Yoga Sūtras of Patañjali formulations as one of the foundations of classical Yoga philosophy of Hinduism.
The Mahābhāṣya ("great commentary") of Patañjali on the Aṣṭādhyāyī of Pāṇini is a major early exposition on Pāṇini, along with the somewhat earlier Varttika by Katyayana. 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. These issues in the word-meaning relation (symbol) would be elaborated in the Sanskrit linguistic tradition, in debates between the Mimamsa, Nyaya and Buddhist schools over the next fifteen centuries.
Patanjali also defines an early notion of sphota, which would be elaborated considerably by later Sanskrit linguists like Bhartrihari. In Patanjali, a sphoTa (from sphuT, spurt/burst) is the invariant quality of speech. The noisy element (dhvani, audible part) can be long or short, but the sphoTa remains unaffected by individual speaker differences. Thus, a single letter or 'sound' (varNa) such as k, p or a is an abstraction, distinct from variants produced in actual enunciation. This concept has been linked to the modern notion of phoneme, the minimum distinction that defines semantically distinct sounds. Thus a phoneme is an abstraction for a range of sounds. However, in later writings, especially in Bhartrihari (6th century CE), the notion of sphoTa changes to become more of a mental state, preceding the actual utterance, akin to the lemma.
Patañjali's writings also elaborate some principles of morphology (prakriyā). In the context of elaborating on Pāṇini'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 Pāṇini which were interpreted somewhat differently in Katyayana.
Unlike Pāṇini'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, although a close examination of actual Sanskrit usage by Woods showed no similarities in language or terminology.
The text of the Mahābhāṣya was first critically edited by the 19th-century orientalist Franz Kielhorn, who also developed philological criteria for distinguishing Kātyāyana's "voice" from Patañjali's. Subsequently, a number of other editions have come out, the 1968 text and translation by S.D. Joshi and J.H.F. Roodbergen often being considered definitive. Regrettably, the latter work is incomplete.
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.
Patanjali is also the reputed author of a medical text called Patanjalah, also called Patanjala or Patanjalatantra. This text is quoted in many yoga and health-related Indian texts. Patanjali is called a medical authority in a number of Sanskrit texts such as Yogaratnakara, Yogaratnasamuccaya, Padarthavijnana, Cakradatta bhasya. Some of these quotes are unique to Patanjala, but others are also found in major Hindu medical treatises such as Charaka Samhita and Sushruta Samhita.
There is a fourth scholar also named Patanjali, who likely lived in 8th-century CE and wrote a commentary on Charaka Samhita and this text is called Carakavarttika. The two medical scholars named Patanjali may be the same person, but generally accepted to be completely different person than the Patanjali who wrote the Sanskrit grammar classic Mahabhasya.