Gnosis is the common Greek noun for knowledge (γνῶσις, gnōsis, f.). The term was used among various Hellenistic religions and philosophies in the Greco-Roman world. It is best known for its implication within Gnosticism, where it signifies a spiritual knowledge or insight into humanity's real nature as divine, leading to the deliverance of the divine spark within humanity from the constraints of earthly existence.
Gnosis is a feminine Greek noun which means "knowledge" or "awareness." It is often used for personal knowledge compared with intellectual knowledge (εἴδειν eídein), as with the French connaître compared with savoir, the Portuguese conhecer compared with saber, the Spanish conocer compared with saber, the Italian conoscere compared with sapere, the German kennen rather than wissen, or the Modern Greek γνωρίζω compared with ξέρω.
A related term is the adjective gnostikos, "cognitive", a reasonably common adjective in Classical Greek. The terms do not appear to indicate any mystic, esoteric or hidden meaning in the works of Plato, but instead expressed a sort of higher intelligence and ability analogous to talent.
Plato The Statesman 258e
In the Hellenistic era the term became associated with the mystery cults.
In the Acts of Thomas, translated by G.R.S. Mead, the "motions of gnosis" are also referred to as "kingly motions".
Irenaeus used the phrase "knowledge falsely so-called" (pseudonymos gnosis, from 1 Timothy 6:20) for the title of his book On the Detection and Overthrow of False Knowledge, that contains the adjective gnostikos, which is the source for the 17th-century English term "Gnosticism".
The difference and meaning of epignosis (ἐπίγνωσις) contrasted with gnosis is disputed. One proposed distinction is between the abstract and absolute knowledge (gnosis) and a practical or more literal knowledge (epignosis). Other interpretations have suggested that 2 Peter is referring to an "epignosis of Jesus Christ", what J.B. Lightfoot described as a "larger and more thorough knowledge".