moderator

noun

Etymology: Learned borrowing from Latin moderātor. First attested as Middle English moderatour. By surface analysis, moderate + -or.

1. Someone who moderates.

   “Angling was […] a moderator of passions.”

   “Instead of focusing on the stressors, as in most research on caregiving, it may be wise to focus on the likely moderators: coping, and social support between stressors and stress. It is often difficult to help an individual to solve his or her primary problem, whereas providing social support and improving coping ability is feasible.”

2. Someone who moderates.
3. Someone who moderates.
4. Someone who moderates.

   “The post was eventually removed by the subreddit’s moderators as potentially fake, but not before a screenshot of it went viral on Twitter and dozens of outlets circulated the story with headlines like “Girl Gets Sweet, Fiery Revenge on Ex With ‘Game of Thrones’ Spoilers.” […] Before r/relationships, Anne was a moderator in the similar but much more unruly r/relationship_advice, where she had to teach herself how to do the job.”

5. The person who presides over a synod of a Presbyterian church.
6. A substance (often water or graphite) used to decrease the speed of fast neutrons in a nuclear reactor and hence increase likelihood of fission.
7. A device used to deaden some of the noise from a firearm, although not to the same extent as a suppressor or silencer.
8. An examiner at Oxford and Cambridge universities.

   “One hall called Civil Law Hall or School, flouriſhed about this time (though in its buildings decayed) by the care of the learned and judicious Dr. Will. Warham Principal or Moderator thereof […]”

9. At the University of Dublin, either the first (senior) or second (junior) in rank in an examination for the degree of Bachelor of Arts.
10. Someone who supervises and monitors the setting and marking of examinations by different people to ensure consistency of standards.
11. A mechanical arrangement for regulating motion in a machine, or producing equality of effect.
12. A kind of lamp in which the flow of the oil to the wick is regulated.