Sampajañña

Sampajañña (Pāli; Skt.: saṃprajanya, Tib: shes bzhin) is a term of central importance for meditative practice in all Buddhist traditions. It refers to "The mental process by which one continuously monitors one's own body and mind. In the practice of śamatha, its principal function is to note the occurrence of laxity and excitation." It is very often found in the pair 'mindfulness and introspection' or 'mindfulness and clear comprehension) (Pali: Sati sampajañña, Skt.: smṛti saṃprajanya).

Sampajañña has been variously translated into English as "continuity", "clear comprehension", "clear knowing", "constant thorough understanding of impermanence", "fully alert" or "full awareness", "attention, consideration, discrimination, comprehension, circumspection", and "introspection".

Princeton Dictionary of Buddhism entry
The Princeton Dictionary of Buddhism entry says;

""saṃprajanya. (P. sampajañña; T. shes bzhin; C. zhengzhi; J. shōchi; K. chŏngji正知 ). In Sanskrit, "clear comprehension," "circumspection," "introspection"; a term that is closely related to, and often appears in compound with, mindfulness (S. SM Ṛ TI, P. sati). In descriptions of the practice of developing meditative absorption ( DHYĀNA ), sm ṛ ti refers to the factor of mindfulness that ties the mind to the object, while sa ṃ prajanya is the factor that observes the mind to determine whether it has strayed from its object. Specifically, Pāli sources refer to four aspects of clear comprehension, which involve the application of mindfulness in practice. The first is purpose (P. sātthaka), viz., whether the action will be in the best interests of oneself and others; its principal criterion is whether it leads to growth in dharma. Second is suitability (P. sappāya): whether an action is in accord with the appropriate time, place, and personal capacity; its principal criterion is skillfulness in applying right means (P. upāyakosalla; S. UPĀYAKAUŚALYA ). Third is the domain of meditation (gocara): viz., all experiences should be made a topic of mindful awareness. Fourth is nondelusion (asammoha): viz., recognizing that what seem to be the actions of a person are in fact an impersonal series of mental and physical processes; this aspect of sa ṃ prajanya helps to counteract the tendency to view all events from a personal point of view. Sa ṃ prajanya thus expands upon the clarity of thought generated by mindfulness by incorporating the additional factors of correct knowledge ( JÑĀNA ) or wisdom ( PRAJÑĀ ).""

From the Pali Canon
Clear comprehension is most famously invoked by the Buddha in tandem with mindfulness practice in the Satipaṭṭhāna Sutta:

"Herein (in this teaching) a monk lives contemplating the body in the body, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief; he lives contemplating feelings in feelings, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief; he lives contemplating consciousness in consciousness, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief; he lives contemplating mental objects in mental objects, ardent, clearly comprehending and mindful, having overcome, in this world, covetousness and grief."

Clear comprehension develops out of mindfulness of breathing (ānāpānasati) and is subsequently present in tandem with mindfulness for all four satipaṭṭhāna-s.

Canonical commentary
While the nikayas do not elaborate on what the Buddha meant by sampajañña, the Pali commentaries analyze it further in terms of four contexts for one's comprehension:
 * purpose (Pāli: sātthaka): refraining from activities irrelevant to the path.
 * suitability (sappāya): pursuing activities in a dignified and careful manner.
 * domain (gocara): maintaining sensory restraint consistent with mindfulness.
 * non-delusion (asammoha): seeing the true nature of reality (see three characteristics).

Critical to Right Mindfulness' purpose (Nyanaponika)
In a correspondence between Bhikkhu Bodhi and B. Alan Wallace, Bhikkhu Bodhi described Ven. Nyanaponika Thera's views on "right mindfulness" and  as follows,
 * ... I should add that Ven. Nyanaponika himself did not regard "bare attention" as capturing the complete significance of ', but as representing only one phase, the initial phase, in the meditative development of right mindfulness. He held that in the proper practice of right mindfulness, sati has to be integrated with ', clear comprehension, and it is only when these two work together that right mindfulness can fulfill its intended purpose.