In Buddhism, Bodhisattva (// BOH-dee-SUT-və) is the Sanskrit term for anyone who has generated Bodhicitta, a spontaneous wish and compassionate mind to attain Buddhahood for the benefit of all sentient beings. Bodhisattvas are a popular subject in Buddhist art.
In early Buddhism, the term bodhisattva was primarily used to refer specifically to Gautama Buddha in his former life. The Jataka tales, which are the stories of the Buddha's past lives, depict the various attempts of the bodhisattva to embrace qualities like self-sacrifice and morality.
According to the Jataka tales, the term "bodhisattva" originally referred to the pre-enlightened practitioner of austerities that surpassed Śrāvakayana and Pratyekabuddhayana by far and completed Bodhisattvayana. Mount Potalaka, for example, is one of Bodhisattvayana. The term for practitioners who have not yet reached Bodhisattvayana was not fixed, but the terms Śrāvaka-Bodhisattva (聲聞菩薩) and Pratyekabuddha-Bodhisattva (縁覚菩薩) had already appeared in the Āgama scriptures of early Indian Buddhism.
Mahayana Buddhism did not place much emphasis in honoring Śrāvakayana and Pratyekabuddhayana since they were classified as part of the Hinayana, but praise of the general Bodhisattvayana was commonplace. Because Hinayana was disliked and the terms Śrāvaka-Bodhisattva or Pratyekabuddha-Bodhisattva were not widely used, while usage of the general term "bodhisattva" had grown in popularity. Nevertheless, "bodhisattva" retained an implied reference to someone on the path to become an arhat or pratyekabuddha. In contrast, the goal of Mahayana's bodhisattva path is to achieve Samyaksambodhiṃ. 
In Theravada Buddhism, the equivalent Pali term bodhisatta is used in the Pāli Canon to refer to Gautama Buddha in his previous lives and as a young man in his current life in the period during which he was working towards his own liberation. During his discourses, to recount his experiences as a young aspirant he regularly uses the phrase "When I was an unenlightened bodhisatta..." The term therefore connotes a being who is "bound for enlightenment", in other words, a person whose aim is to become fully enlightened. In the Pāli canon, the bodhisatta is also described as someone who is still subject to birth, illness, death, sorrow, defilement, and delusion. Some of the previous lives of the Buddha as a bodhisattva are featured in the Jataka tales.
According to the Theravāda monk Bhikkhu Bodhi, the bodhisattva path is not taught in the earliest strata of Buddhist texts such as the Pali Nikayas (and their counterparts such as the Chinese Āgamas) which instead focus on the ideal of the Arahant. In later Theravada literature, the term "bodhisatta" is used fairly frequently in the sense of someone on the path to liberation. The later tradition of commentary also recognizes two additional types of bodhisattas: the paccekabodhisatta, who will attain Paccekabuddhahood, and the savakabodhisatta, who will attain enlightenment as a disciple of a Buddha. In the 1st-2nd century BCE Sri Lankan work, the Buddhavamsa, the idea of the person who makes a Bodhisatta vow to become a fully enlightened Buddha out of compassion for all sentient beings is presented. Another related concept outlined in the Buddhavamsa and in another text called the Cariyapitaka is the need to cultivate certain Bodhisatta perfections or paramitas
Kings of Sri Lanka were often described as bodhisattvas, starting at least as early as Sirisanghabodhi (r. 247-249), who was renowned for his compassion, took vows for the welfare of the citizens, and was regarded as a mahāsatta (Sanskrit mahāsattva), an epithet used almost exclusively in Mahayana Buddhism. Many other Sri Lankan kings from the 3rd until the 15th century were also described as bodhisattvas and their royal duties were sometimes clearly associated with the practice of the Ten Pāramitās.
Theravadin bhikkhu and scholar Walpola Rahula stated that the bodhisattva ideal has traditionally been held to be higher than the state of a śrāvaka not only in Mahayana but also in Theravada Buddhism. He also quotes the 10th century king of Sri Lanka, Mahinda IV (956-972 CE), who had the words inscribed "none but the bodhisattvas will become kings of a prosperous Lanka," among other examples.
But the fact is that both the Theravada and the Mahayana unanimously accept the Bodhisattva ideal as the highest...Although the Theravada holds that anybody can be a Bodhisattva, it does not stipulate or insist that all must be Bodhisattva which is considered not practical.— Walpola Rahula, Bodhisattva Ideal in Buddhism
Paul Williams writes that some modern Theravada meditation masters in Thailand are popularly regarded as bodhisattvas.
Cholvijarn observes that prominent figures associated with the Self perspective in Thailand have often been famous outside scholarly circles as well, among the wider populace, as Buddhist meditation masters and sources of miracles and sacred amulets. Like perhaps some of the early Mahāyāna forest hermit monks, or the later Buddhist Tantrics, they have become people of power through their meditative achievements. They are widely revered, worshipped, and held to be arhats or (note!) bodhisattvas.
According to Jeffrey Samuels, it "may more accurately portray the differences that exist between the two yanas by referring to Mahayana Buddhism as a vehicle in which the bodhisattva ideal is more universally applied, and to Theravada Buddhism as a vehicle in which the bodhisattva ideal is reserved for and appropriated by certain exceptional people."
Mahāyāna Buddhism is based principally upon the path of a bodhisattva. According to Jan Nattier, the term Mahāyāna ("Great Vehicle") was originally even an honorary synonym for Bodhisattvayāna, or the "Bodhisattva Vehicle." The Aṣṭasāhasrikā Prajñāpāramitā Sūtra contains a simple and brief definition for the term bodhisattva, which is also the earliest known Mahāyāna definition. This definition is given as the following.
Because he has enlightenment as his aim, a bodhisattva-mahāsattva is so called.
The earliest depiction of the Bodhisattva path in texts such as the Ugraparipṛcchā Sūtra describe it as an arduous, difficult monastic path suited only for the few which is nevertheless the most glorious path one can take. Three kinds of Bodhisattvas are mentioned in the early Mahayana texts: the forest, city, and monastery Bodhisattvas - with forest dwelling being promoted a superior, even necessary path in sutras such as the Ugraparipṛcchā and the Samadhiraja sutras. The early Rastrapalapariprccha sutra also promotes a solitary life of meditation in the forests, far away from the distractions of the householder life. The Rastrapala is also highly critical of monks living in monasteries and in cities who are seen as not practicing meditation and morality. The Ratnagunasamcayagatha also says the Bodhisattva should undertake ascetic practices (dhutanga), "wander freely without a home", practice the paramitas and train under a guru in order to perfect his meditation practice and realization of prajnaparamita. These texts seem to indicate the initial Bodhisattva ideal was associated with a strict forest asceticism.
Mahāyāna Buddhism encourages everyone to become bodhisattvas and to take the bodhisattva vows. With these vows, one makes the promise to work for the complete enlightenment of all sentient beings by practicing the six perfections. Indelibly entwined with the bodhisattva vow is merit transference (pariṇāmanā).
In the Lotus Sūtra, life in this world is compared to people living in a house that is on fire. People take this world as reality pursuing worldly projects and pleasures without realizing that the house is ablaze and will soon burn down (due to the inevitability of suffering). A bodhisattva is one who has a determination to free sentient beings from samsara and its cycle of death, rebirth and suffering. This type of mind is known as the mind of awakening (bodhicitta).
A commonly repeated misconception in Western literature is that bodhisattvas delay their own liberation. This confusion is based on a misreading of several different scriptural concepts and narratives. One of these is the Tibetan teaching on three types of motivation for generating bodhicitta. According to Patrul Rinpoche's 19th century Words of My Perfect Teacher (Kun bzang bla ma'i gzhal lung), a bodhisattva might be motivated in one of three ways. They are:
These three are not types of people, but rather types of motivation. According to Patrul Rinpoche, the third quality of intention is most noble though the mode by which buddhahood actually occurs is the first; that is, it is only possible to teach others the path to enlightenment once one has attained enlightenment oneself.  The ritualized formulation of the bodhisattva vow also reflects this order (becoming a buddha so that one can then teach others to do the same). A bodhisattva vow ritual text attributed to Nāgārjuna, of the second-third century CE, states the vow as follows: "Just as the past tathāgata arhat samyaksambuddhas, when engaging in the behavior of a bodhisattva, generated the aspiration to unsurpassed complete enlightenment so that all beings be liberated, all beings be freed, all beings be relieved, all beings attain complete nirvana, all beings be placed in omniscient wisdom, in the same way, I whose name is so-and-so, from this time forward, generate the aspiration to unsurpassed complete enlightenment so that all beings be liberated, all beings be freed, all beings be relieved, all beings attain complete nirvana, all beings be placed in omniscient wisdom." 
Another reason for the misconception that a bodhisattva "delays" Buddhism is that a bodhisattva rejects the liberation of the śravaka and pratyekabuddha, described in Mahāyāna literature as either inferior (as in Asaṅga's fourth century Yogācārabhūmi) or nonexistent (as in the Lotus Sūtra).  That a bodhisattva has the option to pursue such a lesser path, but instead chooses the long path towards buddhahood is one of the five criteria for one to be considered a bodhisattva. The other four are: being human, being a man, making a vow to become a buddha in the presence of a previous buddha, and receiving a prophecy from that buddha.
The six perfections that constitute bodhisattva practice should not be confused with the actual acts of benefiting beings that the bodhisattva vows to accomplish once he or she is a buddha. The six perfections are a mental transformation and need not actually benefit anyone. This is seen in the story of Vessantara, an incarnation of Śākyamuni Buddha while he was still a bodhisattva, who commits the ultimate act of generosity by giving away his children to an evil man who mistreats them. Vessantara's actual acts do not benefit beings; in fact, he causes direct harm. However, the merit from his perfection of generosity fructifies in his lifetime as Śākyamuni Buddha when he attains complete enlightenment. 
According to many traditions within Mahāyāna Buddhism, on the way to becoming a Buddha, a bodhisattva proceeds through ten, or sometimes fourteen, grounds or bhūmis. Below is the list of the ten bhūmis and their descriptions according to the Avataṃsaka Sūtra and The Jewel Ornament of Liberation, a treatise by Gampopa, an influential teacher of the Tibetan Kagyu school. (Other schools give slightly variant descriptions.)
Before a bodhisattva arrives at the first ground, he or she first must travel the first two of five paths:
The ten grounds of the bodhisattva then can be grouped into the next three paths
The chapter of ten grounds in the Avataṃsaka Sūtra refers to 52 stages. The 10 grounds are:
After the ten bhūmis, according to Mahāyāna Buddhism, one attains complete enlightenment and becomes a Buddha.
With the 52 stages, the Śūraṅgama Sūtra recognizes 57 stages. With the 10 grounds, various Vajrayāna schools recognize 3–10 additional grounds, mostly 6 more grounds with variant descriptions.
Some sutras said a beginner would take 3–22 countless eons (mahāsaṃkhyeya kalpas) to become a buddha. Pure Land Buddhism suggests buddhists go to the pure lands to practice as bodhisattvas. Tiantai, Huayan, Zen and Vajrayāna schools say they teach ways to attain buddhahood within one karmic cycle.
Various traditions within Buddhism believe in specific bodhisattvas. Some bodhisattvas appear across traditions, but due to language barriers may be seen as separate entities. For example, Tibetan Buddhists believe in various forms of Chenrezig, who is Avalokiteśvara in Sanskrit, Guanyin in China, Gwan-eum in Korea, Quan Am in Vietnam, and Kannon in Japan. Followers of Tibetan Buddhism consider the Dalai Lamas and the Karmapas to be an emanation of Chenrezig, the Bodhisattva of Compassion.
Kṣitigarbha is another popular bodhisattva in Japan and China. He is known for aiding those who are lost. His greatest compassionate vow is:
If I do not go to the hell to help the suffering beings there, who else will go? ... if the hells are not empty I will not become a Buddha. Only when all living beings have been saved, will I attain Bodhi.
The place of a bodhisattva's earthly deeds, such as the achievement of enlightenment or the acts of Dharma, is known as a bodhimaṇḍa, and may be a site of pilgrimage. Many temples and monasteries are famous as bodhimaṇḍas. Perhaps the most famous bodhimaṇḍa of all is the Bodhi Tree under which Śākyamuṇi achieved buddhahood. In the tradition of Chinese Buddhism, there are four mountains that are regarded as bodhimaṇḍas for bodhisattvas, with each site having major monasteries and being popular for pilgrimages by both monastics and laypeople. These four bodhimandas are:
4 Great Bodhisattvas (in Chinese Buddhism)
四大菩薩. (菩薩 is short for菩提薩埵)
In this order: Compassion, Wisdom, Vow and Practice.
悲 智 願 行
1, Avalokitesvara Bodhisattva 觀世音 菩薩 short: 觀音 菩薩
Stands for Great Compassion.
2, Manjusri Bodhisattva 文殊師利 菩薩 short: 文殊 菩薩
Stands for Great Wisdom.
3, Ksitigarbha Bodhisattva 地藏王 菩薩 short: 地藏 菩薩
Stands for Great Vow.
4, Samantabhadra Bodhisattva 普賢 菩薩
Stands for Great Practice.
Standing bodhisattva. Gandhāra, 2nd-3rd century.
Mural of bodhisattvas. China, Tang Dynasty.
Ākāśagarbha Bodhisattva. Japan, 9th century.
Avalokiteśvara Bodhisattva. India, 11th-12th century.
Mahāsthāmaprāpta Bodhisattva. China, 13th century.
Youthful Mañjuśrī Bodhisattva silver statue. Java, 9th century Indonesia.
Mañjuśrī Bodhisattva crossing the sea. Japan, 14th century.
Kṣitigarbha Bodhisattva. Japan, 15th century.
Samantabhadra Bodhisattva. Japan.
Maitreya Bodhisattva. Thiksey Monastery, Ladakh, India
Shrine with an Image of a Bodhisattva. Brooklyn Museum
...the term Bodhisattva, or Wisdom-being, first used of Gautama between the Going-forth and the attainment of Nibbāna, came to mean a Buddha-designate....
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