player
A person who takes part in a game or sport.
A player is someone who participates in a game or sport. When you sit down for a board game, everyone at the table is a player. On a soccer field, there are eleven players on each team. In chess, there are two players facing off across the board.
The word applies to both casual and serious contexts. Kids playing tag at recess are players, but so are professional athletes competing in the Olympics. Video game enthusiasts are players whether they're playing for fun or competing in tournaments for prize money.
In music, a player is someone who performs on an instrument. A piano player or guitar player makes music, though musicians more commonly call themselves pianists or guitarists.
The word can also describe someone's role in events or situations. A key player in a school project is someone whose contributions really matter. In history, we might say George Washington was a major player in America's founding.
A player can also be a machine that plays music or videos, like a cassette player or a DVD player.