OSIS By N., Sam M.S. - 16 1. an ill state. 2. procedure or condition. 3. development or growth. OSIS: "One of the first suffixes most medical terminology students are introduced to is -osis." Related Psychology Terms DREAM-STATE (D-STATE, REM- STATE) Piaget’s Theory of Cognitive Development ADOLESCENCE (Theories) AMERICAN PSYCHIATRIC ASSOCIATION LEGAL PSYCHIATRY (Forensic Psychiatry) NATIONAL INSTITUTE OF MENTAL HEALTH (NIMII) JOINT COMMISSION ON MENTAL ILLNESS AND HEALTH Comparison of Assessment Tools CHILD PSYCHOLOGY GESELL, ARNOLD LUCIUS (1880- 1961) Cite this page: N., Sam M.S., "OSIS," in PsychologyDictionary.org, April 7, 2013, https://psychologydictionary.org/osis/ (accessed December 9, 2022).