precession / presession [prəˈsɛʃən]
precession – n. – 1. an advance; 2. Astronomy – the slow retrograde movement of the equinoctial points resulting in an earlier equinox each year caused by a slow change in the direction of the earth’s axis; 3. Physics – the slow rotation of the axis of a gyroscope, or other object; 4. an action or fact coming before in time, order or rank; 5. Phonetics – the changing in voicing of a vowel towards a more closed sound
presession – n. – 1. presidence – the action of exercising authority or control over a meeting, gathering, council etc.; 2. the time before a course, term, treatment or other event occurs, preliminary event(s)