The Sanskrit word Ekayāna means 'one path' or 'one vehicle'. It is also referred to as 'Buddha-yāna'.
In the hinduist Brihadaranyaka - Upanishad (II.iv.11 and IV.v.12) of the Shukla - Yajurveda the word Ekayāna is mentioned in the meaning of 'spiritual journey'.
In the Satipatthana-Sutta of the Pali Canon, a similar term ekāyana is used, which is translated by default with 'a single path' or 'direct path', while ekayāna (or buddha-yāna) is the one vehicle, the speculative one integral path, which is emphasized in some lineages, who see the variety of the existing directions as branches of the one tree or path, which the Buddha has once taught.
According to the Vajrayana, the Buddha taught 84,000 teachings, which is probably to suggest that the doctrine covers everything, or to symbolize the boundlessness of the teachings of the Buddha.
In japanese Buddhism, the Ekayana forms the basis of the doctrine of the Hua Yen or Kegon scool, of the Zen and of the Tendai School.
To the Ekayana sutras of the Mahayana belong among others the Lankavatara Sutra, the Avatamsaka Sutra (Flower garland Sutra), the Lotus Sutra (White Lotus of the True Dharma), the Shurangama Sutra, the Srīmālādevī Simhanada Sūtra (The Roar of the Lion of Queen Srimala), the Sraddhotpanna Sutra, the Satipaṭṭhāna Sutta (Nikayas ) and the Mahaparinirvana Sutra.
In the Lankavatara - Sutra can be read: 'In fact, there is no list of vehicles. Therefore I speak of one vehicle; but for the purpose of transporting the ignorants I speak of the variety of vehicles.
The Lotus Sutra compares the Ekayana with a white oxcart.
In the Shrîmâlâdevîsimhanâda-sûtra, a woman explains the doctrine of Tathâgatagarbha(Buddha-Nature). This Sûtra condenses to the doctrine of the One Vehicle (ekayâna).
* From a universal point of view, Buddha's lifestory can be interpreted as 20 steps of the 22-stepped 'one path' .
Already from the multitude of different details of the different versions of the curriculum vitae, as well as from the version of the Tibetan Mūlasarvāstivāda-vinaya, it can be seen that some schools must have known this integral path, whose targeted practice is a clever means (Upaya) to go the path faster and easier.
* The 52 chapters of the Gandavyuha-Sutra are another example of a veiled desciption of steps 1 to 19 of the universal path, which also contains the other religions.