/ ˈkɒmənteɪtə(r); NAmE ˈkɑːm-/ noun commentator (on sth)
1.
a person who is an expert on a particular subject and talks or writes about it on television or radio, or in a newspaper :
a political commentator
2.
a person who describes an event while it is happening, especially on television or radio :
a television / sports commentator
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WORD ORIGIN
late Middle English : from Latin , from commentari , frequentative of comminisci devise.