Tennis trading glossary: every word explained

This is a plain glossary of the words you'll meet when trading tennis on a prediction market, from "break" and "tiebreak" to "spread", "slippage" and "50-50 resolution". Each entry is a few sentences. Where there's a fuller article, I link to it. If you're new, read the beginner's guide first and keep this page open while you do.

Match words

Ace

A serve the receiver can't touch. Aces are the quickest way to hold serve, and a player hitting a lot of them is hard to break. Prices barely move on an ace unless it's a big point.

Hold

Winning a game on your own serve. On the men's tour, servers hold about 80% of the time on hard courts, less on clay and more on grass. Holds are expected, so they move the price only a little. Serve-hold rates are the main input to the win-chance calculator.

Break (of serve)

Winning a game on your opponent's serve. Because holds are the norm, a break is the big event in a set, and the price jumps when one happens. How much it jumps is the subject of why the price jumps on a break of serve.

Break back

Winning your opponent's serve straight after they've broken yours, which cancels the break. When it happens, the price usually goes back to where it was before the first break.

Break point

A point which, if the receiver wins it, breaks serve. Prices move more on break points than on ordinary points, because the next point can change the set.

Consolidate

Holding your own serve right after breaking your opponent's. It makes the break stick and nudges the price a little further in your favour.

Deuce and advantage

At 40-40 the game is at deuce. A player then needs two points in a row to win it. The first gives them the advantage; the second wins the game. Long deuce games feel dramatic but count as one game.

Tiebreak

A short game played at 6-6 in a set, first to seven points with a two-point lead. Each point decides a big share of the set, so the price can move 10¢ or more on a single point. See trading tiebreaks.

Deciding set

The last possible set: the third in a best-of-three match, the fifth in a best-of-five. Every game in it is worth a lot, and a late break can move the price by 30 or 40¢.

Best of three, best of five

How many sets a match can go to. Most matches are best of three. Men's matches at the four majors are best of five, which makes early setbacks less costly and the match slower to decide.

Serve-hold percentage

How often a player wins their own service games. It's the single most useful number for guessing how a match will go, and it's what my price model runs on. Roughly 80% for ATP hard courts, 65% for WTA.

Momentum

The feeling that a player is on a run. Prices react to it, sometimes too much. My data on big swings suggests a sharp move is more likely to continue than reverse in the next few minutes, but neither is certain.

Market words

Price

What one share costs, in cents from 1 to 99. It's the market's estimate of a player's chance of winning. A player at 62¢ is being given about a 62% chance. The basics are in how tennis prices work.

Implied probability

The price turned into a percentage. 62¢ implies 62%. On a prediction market the two players' prices add up to about 100%, unlike a bookmaker's odds, which add up to more.

Share

One unit of a player. It pays $1 if that player wins the match and $0 if they lose. Your shares are your stake divided by the price: $31 at 62¢ buys 50 shares.

Stake

The money you put into a trade. On a prediction market, it's also the most you can lose on it.

Spread

The gap between the price you can buy at and the price you can sell at. It's a cost you pay the moment you trade. Busy matches have a spread of a cent or two; quiet ones can be much wider.

Liquidity

How much money is waiting to trade at prices near the current one. A liquid market lets you buy or sell a decent size without moving the price. Small tournaments often have very little.

Slippage

The difference between the price you expected and the price you actually got, usually because your order was bigger than what was on offer at the best price. It's worst on thin markets and during fast moves.

Market order and limit order

A market order fills straight away at the best price available. A limit order names a price and waits. On Polymarket, only orders that fill immediately pay a fee.

Maker and taker

The maker is the person whose order waits on the book. The taker is the one who accepts it. Polymarket charges takers a fee and makers nothing. Details in Polymarket tennis fees explained.

Fee

What Polymarket charges on a taker order: shares × 5% × price × (1 minus price), when I checked in October 2026. It's biggest at 50¢. The 77 Tennis demo has no fee.

Settlement, resolution

What happens when the match ends: the market is resolved from the official result, winning shares pay $1 and losing shares pay $0. On the demo, winnings land in your balance automatically.

50-50 resolution

A market that pays 50¢ on every share instead of picking a winner. On Polymarket's tennis markets it happens for walkovers, cancelled matches, and matches with no winner within 14 days of the scheduled start.

Favourite and underdog

The favourite is the player priced above 50¢; the underdog is the other one. On the 77 Tennis board the favourite is shown in green and the underdog in red, by ranking when it's known and by price when it isn't.

Trading words

Take profit

An instruction to sell automatically once your gain reaches a level you set. It locks in a good position without you watching every point. See take-profit and stop-loss.

Stop loss

An instruction to sell automatically once your loss reaches a level you set. In tennis the price can jump straight past your level, so a stop limits damage rather than fixing it exactly.

Sell all

Closing every open position at the current prices in one go. On the 77 Tennis board it's one button, and the take-profit and stop-loss settings at the top of the page use it.

Open P&L and realized P&L

Open P&L is what your current positions are worth compared with what you paid. Realized P&L is the profit or loss you've actually banked by selling or settling. Only realized P&L counts on the leaderboard.

Equity

Your cash plus what your open positions are worth right now. It's the number that tells you how you're really doing.

Break-even price

The sell price at which you get back exactly what you paid, including fees. Without fees it's your buy price. With fees on both sides it's a little higher. The profit calculator works it out.

Overreaction

A price move bigger than the score justifies, usually after something dramatic. Traders look for these, but my data shows most big moves keep going for a while rather than snapping back, so be careful.

Results and rules

Retirement

A player stops during the match because of injury or illness. On Polymarket's tennis markets, the player who advances wins the market, even if only one point was played. Full details in what happens if a player retires.

Walkover

A player withdraws before the match starts and the opponent advances without playing. Polymarket's tennis markets resolve 50-50 on a walkover, so a favourite you bought at 85¢ pays back only 50¢.

Default

A player is removed from a match by the umpire, for example for dangerous conduct. The market treats it like a retirement: the player who advances wins.

Suspended match

Play stops, for rain, bad light or a curfew, and resumes later, sometimes the next day. The market stays open and your position stays in place. Momentum often resets when play restarts.

Qualifier

A player who earned a main-draw place by winning qualifying matches in the days before the event. They're match-sharp, which is one reason early-round upsets happen.

Seed

A player ranked highly enough to be placed in the draw so that top players don't meet early. Seeds are usually heavy favourites in the first rounds, but not always safe ones.

Round robin

A group format where each player plays everyone in their group, used at the ATP Finals. A player can lose a match and still win the event, which changes what some matches are worth to the players.

Dead rubber

A round-robin match that can't change who qualifies from the group. One or both players may have less to play for, and the price often reflects that.

The words in one trade

A word I haven't covered?

Email me at hello@77tennis.com and I'll add it. The best way to make these words stick is to use them: the 77 Tennis demo gives you $1,000 of play money and the same live prices, so you can watch a break, a tiebreak and a settlement happen for yourself without risking a cent.

FAQ

What's the difference between a retirement and a walkover?

A retirement happens after the match has started and pays the player who advances. A walkover happens before it starts and resolves 50-50 on Polymarket's tennis markets.

What does a price of 62 cents mean?

That the market gives the player about a 62% chance of winning. Each share costs 62¢ and pays $1 if they win.

What's the difference between open and realized profit and loss?

Open P&L is the paper gain or loss on positions you still hold. Realized P&L is what you've actually banked by selling or settling. The 77 Tennis leaderboard only counts realized P&L.

Why does the spread matter?

Because you buy at the higher price and sell at the lower one, so a wide spread means the price has to move in your favour before you've made anything. On small matches it can cost more than the fee.