The origins are debated, but the most popular theory traces back to medieval France. A clock face was used to track scores — the hand moved to 15, 30, and 45 minutes. "45" was later shortened to "40" for simplicity. Zero was called "love," possibly from the French word "l'oeuf" (the egg), symbolizing a zero shape.

Deuce occurs when both players reach 40-40 in a game. From deuce, a player must win two consecutive points to win the game. The first point won after deuce gives that player "Advantage" (AD). If the player with advantage wins the next point, they win the game. If they lose it, the score returns to deuce.

A tiebreak is played when the set score reaches 6-6. In a standard tiebreak (also called a "7-point tiebreak"), players compete to reach 7 points with a 2-point lead (e.g., 7-5, 8-6, 9-7). Points are counted numerically (1, 2, 3...) instead of 15-30-40. The server rotates every 2 points.

A player must win 6 games and be ahead by at least 2 games to win a set. Possible set scores include 6-0, 6-1, 6-2, 6-3, 6-4, or 7-5. If the score reaches 6-6, a tiebreak is played to decide the set (7-6).

Best of 3 sets: The first player to win 2 sets wins the match. Used in most WTA matches, ATP tournaments (non-Grand Slam), and doubles.
Best of 5 sets: The first player to win 3 sets wins. Used in Grand Slam men's singles (Australian Open, French Open, Wimbledon, US Open). Some tournaments use a "super tiebreak" (first to 10 points) in the deciding set.

The same player serves for the entire game. After the game ends, the serve switches to the other player. In a tiebreak, the player who would serve next starts serving for the first point, then serve rotates every 2 points between the players.

This depends on the tournament rules. Most tournaments play a standard tiebreak (to 7 points) at 6-6 in the final set. However, some Grand Slams have unique rules: Wimbledon plays a tiebreak to 7 at 12-12 in the final set; the French Open used to require a 2-game lead with no tiebreak (changed in 2022); the Australian Open plays a "super tiebreak" (first to 10 points) at 6-6 in the final set.

These are fun tennis slang terms! A "bagel" refers to winning a set 6-0 (the "0" looks like a bagel). A "breadstick" is winning a set 6-1 (the "1" resembles a breadstick). A "double bagel" means winning a match 6-0, 6-0 — a complete shutout!