An Etymological Dictionary of Astronomy and Astrophysics

1. Philo.: The doctrine that reality consists of an unchanging whole in which change is mere illusion. → pluralism.
   

2. Philo.: The doctrine that the person consists of only a single substance, or that there is no crucial difference between mental and physical events or properties.
   

3. The attempt to explain anything in terms of one principle only. → dualism, → materalism, → idealism (Dictionary.com).

See also: → mono-; → -ism.