I would like to clarify here what is meant by the term “Hinayāna.” The term means “Small Vehicle” whereas Mahāyāna means “Great Vehicle.” The Mahāyānists referred to those Buddhists who rejected the Mahāyāna sūtras as Hinayāna Buddhists. The so-called Hinayāna Buddhists believed that the Buddha’s teachings could only be found in a closed canonical collection called the Three Baskets (S. tripiṭaka) composed of the sūtras that are the Buddha’s discourses, the monastic rules and procedures (S. vinaya), and the “Higher Dharma” (S. abhidharma) treatises that systematized the teachings in the discourses. The southern recension of these discourses is called the Pāli canon, since it was recorded in the Pāli language. It is composed of five Nikāyas or “Collections.” The northern recension of these discourses was in Sanskrit. They were called the Āgamas or “Sources” and exist now in Chinese translation. Today the Theravādin schools of Southeast Asia and Sri Lanka continue to uphold the Pāli canon as the only authoritative canonical collection of the Buddha’s teachings. The Sarvāstivādin and other northern schools that upheld the Āgama sūtras have long since disappeared in India. Because the term Hinayāna is a disparaging epithet and not the proper name of a school, it is best to use the term Theravāda and not Hinayāna when referring to the Buddhism of Southeast Asia. Calling the Āgama sūtras, their teachings, and the schools that rely upon them Hinayāna, as they are by East Asian Buddhists to this day, is problematic for a couple of reasons. The first is that, as Nichiren points out, those who study these teachings or who belong to these schools may have actually adopted Mahāyāna views. The second problem is that, according to Zhiyi, the teachings introduced in the Āgama sūtras can themselves express the perspective of the Mahāyāna if understood more deeply. Nevertheless, the term Hinayāna can be understood to refer to those teachings and schools that confine themselves to pre-Mahāyāna teachings, perspectives, and motivations, for that is how Nichiren uses the term in Kaimoku-shō.
Open Your Eyes, p163