Styāna (Sanskrit; Tibetan phonetic: mukpa) or thīna (Pali) is a Buddhist term that is translated as "sloth", "lethargy", "gloominess", etc.
In the Mahayana tradition, styāna is defined as a mental factor that causes the mind to be withdrawn, unclear, and unable to focus.
In the Theravada tradition, thīna is said to occur in conjunction with middha (torpor), which is defined as a morbid state that is characterized by unwieldiness, lack of energy, and opposition to wholesome activity.
Styāna or thīna is identified as: Bhikkhu Bodhi explains: Sloth is sluggish or dullness of mind.
As a pair, they constitute one of the five hindrances, which is overcome by initial application (vitakka).The Atthasālinī (II, Book I, Part IX, Chapter II, 255) states about sloth and torpor: “Absence of striving, difficulty through inability, is the meaning.” We then read the following definitions of sloth and torpor: The compound “sloth-torpor” is sloth plus torpor; of which sloth has absence of, or opposition to striving as characteristic, destruction of energy as function, sinking of associated states as manifestation; torpor has unwieldiness as characteristic, closing the doors of consciousness as function, shrinking in taking the object, or drowsiness as manifestation; and both have unsystematic thought, in not arousing oneself from discontent and laziness (or indulgence), as proximate cause.