Citta is the “sum total of mind” (4) or “mind-stuff.” It includes the ego or “I” feeling (ahamkāra), the intellect or discriminative faculty (buddhi), and the desiring part of the mind that is attracted to external objects (manas), which is attracted to external objects.

Guṇas are the three fundamental constituents or qualities of Nature (Prakṛti): sattva (tranquility, illumination), rajas (activity and restlessness), and tamas (inertia and dullness). Their interaction gives rise to the diversity and continual change of the material world.

Īśvara is the supreme Puruṣa, or God, a supreme consciousness that is unaffected by afflictions, actions, or the impressions of desires. Īśvara is the original, eternal teacher of all teachers and sages and is associated with complete spiritual freedom.

Karma is the law of action and its consequences. The three types of karma are prārabdha karma, the portion of past actions experienced in the present life; āgāmi karma, new actions created in the present; and sañcita karma, the accumulated store of past actions awaiting future fulfillment.

Kleśas are the five primary obstacles, or root afflictions, that cause suffering and give rise to karma. They are ignorance of the true Self (avidyā), egoism (asmitā), attachment to pleasure (rāga), aversion to pain (dveṣa), and clinging to bodily life (abhiniveśa).

Defined as “Yoga in practice,” Kriyā Yoga is a preliminary discipline consisting of three key elements. It consists of tapas (accepting pain for purification), svādhyāya (study of spiritual texts), and Īśvara praṇidhāna (surrender to the Supreme Being). This practice is designed to minimize obstacles and prepare the aspirant for the deeper states of meditation.

The mystic sound vibration that is the name and form of Īśvara (God) is “OM.” It is regarded as the primordial sound from which all other sounds arise and is traditionally repeated in meditation.

Prakṛti is the “seen,” or nature, which encompasses the entire objective universe. It is everything other than the Seer (Puruṣa), including the gross elements, sense organs, mind, and intellect. Its purpose is twofold: to provide experiences for the Seer and, through these experiences, to ultimately facilitate the Seer’s liberation from bondage to it.

Pratipakṣa Bhāvana is a practical mental technique for overcoming negative thoughts. When disturbed by a negative thought, one consciously cultivates its opposite, such as love in place of hatred or compassion in place of anger.

Puruṣa is the true Self, the Seer, or pure consciousness. It is the eternal, unchanging subject that witnesses all the activities of the mind and nature (Prakṛti) but remains forever distinct from them. Its true nature is eternal freedom, though it appears bound through ignorance.

Samādhi is contemplation or absorption, the eighth and final limb of Yoga. It is a superconscious state that follows meditation, in which the distinction between the meditator, the process of meditation, and the object of meditation dissolves. The text distinguishes between lower forms of samādhi and nirbīja ("seedless") samādhi, the highest state of liberation.

Saṃyama is the combined and continuous application of the final three limbs of Yoga—concentration (dhāraṇā), meditation (dhyāna), and contemplation (samādhi)—on a single object. By mastering this unified practice, a Yogi can gain complete knowledge of the inner secrets and powers of the object of focus.

The true, eternal Self that is the ultimate knower or witness of all experience is the Seer (Draṣṭuḥ). It is distinct from the body and mind, which it observes as objects. In Yoga philosophy, the Seer is identical with Puruṣa, or pure consciousness.

Tapas is a spiritual austerity or discipline aimed at purifying the body and mind. It involves willingly accepting hardship and practicing self-discipline as a means of spiritual growth.

Vairāgya is non-attachment, which literally means “colorlessness.” It is defined as a conscious state of self-mastery in one who is free from craving for objects and experiences. It is a state of self-mastery that is distinct from indifference or apathy.

The modifications, ripples, or thought-forms that constantly arise in the mind-stuff (citta) are Vṛtti. The five types of vṛttis are right knowledge, misconception, verbal delusion, sleep, and memory.