The prefixes ENTO, endo, and eso all have the same meaning of 'INNER'. ENTO is a four letter prefix derived from the Greek word 'entos', meaning 'WITHIN'. Endo is also a four letter prefix derived from the Greek word 'endon', meaning 'WITHIN'. Lastly, eso is a three letter prefix derived from the Greek word 'esō', meaning 'WITHIN'. All three of these prefixes are used to describe something that is located inside or WITHIN something else.