Om: The Sanskrit (ancient Indian language) word chanted when contemplating ultimate reality. Siddhartha meditates by focusing upon Om repeatedly as a Samana and as the Brahmin's son. Later, he forgets it until, contemplating suicide near the river, it returns and enlightens him. Siddhartha then begins to understand Om as the unity of everything in the world, in a recurring cycle. The voice of the river is this one word, Om.
Self: As a young man, Siddhartha's sense of Self (his individual identity) is arrogant, rejecting his father's Hindu teachings. As a Samana, he denies the desires of his Self to try to understand the world. In Samsara, he embraces his desires for many years and pleasures his body by gambling, drinking, and lovemaking. Only later does he form the identity of his Self as being a part of everything in the world and destroy his selfish ego.
Atman: The thing Siddhartha seeks to understand. Atman is his innermost essence and what he really is inside. First Atman is confused with being his Self, until he senses it is beneath his Self. Siddhartha thinks his Self is merely his body; by destroying his body from fasting and abuse, the Self will be destroyed, and only Atman shall be left. After staying with Vasudeva near the river, he realizes that Atman is his sense of Self as it connects to the rest of the world. Only after his ego is destroyed and his true identity found does he find his innermost essence.
Rig-Veda (Vedas): Four canonical chants called Vedas form a large part of Hindu beliefs. Rig-Veda is one of these, as well as the Sama-Veda, Yajur-Veda, and Atharva-Veda. Siddhartha studies the Vedas under the Brahmin's supervision.
Savathi: The town where Buddha's Jetavana Monastery has been established. Siddhartha goes here with Govinda after leaving the Samanas to hear the Buddha's teachings. Govinda becomes a disciple while Siddhartha continues on his pilgrimage.
Jetavana grove: A gift of Anathapindika, this garden in Savathi houses Buddha's monastery. Many followers come to hear the Buddha teach here, where there are many monks with shaven heads and yellow robes who have become his disciples.
Four main points: The core of Buddha's philosophy, in addition to the eightfold path. The four main points probably refer to his four noble truths: suffering, its cause, cessation, and the way it leads to cessation.
River: Siddhartha crosses the river before entering the sinful town of Samsara. He returns to the river and contemplates suicide by drowning, but his reflection in the water enlightens him. Becoming a ferryman with Vasudeva, Siddhartha learns to hear the voice of the river that is Om, the unity of things, and the river befriends him as if it were a living creature. Vasudeva's face appears to be the river before he dies, flowing endlessly together. The river represents Siddhartha's understanding of life as a flowing of many faces that are all him, all one person unchanging but changing. The river has the 'transitory appearances' that he explains to Govinda, transitory like himself.
Samsara: A town filled with greed, materialism, and lust. Here Siddhartha experiences the sin he had always avoided in the past after being so sheltered by his father the Brahmin. After twenty years, he flees and comes to peace by returning to the river; later his son, Young Siddhartha, runs away from the quiet river to return to Samsara, despite his father's attempts to shelter him from the sorrow he had experienced there. Recognizing that everyone must know sin firsthand before gaining wisdom, Siddhartha gives up trying to 'save him' from Samsara's wickedness.
Songbird: Kamala's rare bird kept in a cage. Siddhartha dreams that this bird had died, thinking that it is his own inner spirit that has been lost. Kamala sets the bird free to fly away after Siddhartha disappears, for she is heartbroken. Later, Siddhartha realizes that the metaphorical songbird within him is in fact very much alive and rejoices that he has found peace.
Nirvana: In Buddhism, this is the absolute state of bliss achieved by destroying one's Self. The highest level of nirvana is reached only at death, although Siddhartha and the Buddha both have reached such a state of bliss after understanding Om and the interrelation of everything in the world. After destroying his selfish ego, Siddhartha finds Atman within and comes very close to nirvana by listening to the river. Govinda has not progressed at all, in spite of his faith in the Buddha's teachings.