Sutra in Sanskrit (or sutta in Pali) literally means a thread. It broadly means a group of expressions of a general truth or principle threaded together to make a teaching. Sutras exist in the Hindu, Jain and Buddhist religions. Within each, there is a definition of what a sutra is, and these vary.

The oldest sutra are those from the Vedas, which predate Buddha’s birth by over a thousand years. Also well known are the Yoga Sutras of Patanjali. Both these sutras are unrelated to Buddhism’s sutras except for the fact they contain spiritual teachings. 

Within Buddhism, the term “sutra” is commonly used to denote the oral teachings given by Buddha Shakyamuni. These typically begin, “Thus have I heard, at one time…”

This is the definition most commonly used by Mahayana¹The latter of the two major schools of Buddhism, it emphasizes the liberation of all sentient beings as opposed to the individual liberation of the Theravada school Buddhists, yet not all sutras fit this definition. The most widely known example is the Heart Sutra, also known as the Mahaprajnaparamita Heart Sutra.

The Heart Sutra is widely regarded as the most distilled essence of Buddha’s teaching on non-duality, yet Buddha himself doesn’t appear in it, nor is he mentioned. Instead, the sutra takes the form of a secret transmission of the revelation of the highest incorruptible truth from the Bodhisattva Avalokiteshvara to Buddha’s closest disciple, Shariputra. So it is not universally true that all Buddhist sutras are Buddha Shakyamuni’s teachings, nor do all of them begin with “Thus have I heard, at one time…”. Most do, but not all, and as the example of the Heart Sutra shows, those that don’t can also be of immense importance and power.