Bump: A player is permitted to ride off another to spoil his shot or to remove him from the play. The angle of contact must be no more than 45 degrees. The faster the pony travels the smaller the angle must be. A good bump can shake discs and dentures loose. 

Chukka: There are six chukkas (periods) in high handicap matches, each lasting seven minutes plus up to 30 seconds of overtime. If, during the extra 30 seconds, the ball hits the sideboards or goes out of bounds, or if the umpire blows his whistle for a foul, the chukka is over. There is no overtime at the end of the final chukka unless the score is tied. Players return to the field each chukka with a fresh pony. Chukka comes from the Indian word for a circle or round.

Divots: Turf kicked up by a ponies' hooves

Ends: The back lines of a polo pitch. Teams change ends, i.e. switch the halves they defend, each time a goal is scored in order to equalize wind and turf conditions.

Equipment: Hard helmets for players are compulsory. Knee-pads, whips and spurs are optional

Field: A full size polo field is 300 yards by 160 yards, or the area of three soccer pitches. The goal posts, which collapse on severe impact, are set eight yards apart. 

Forehand: The most common shot, used to hit the ball forwards. The Offside forehand is th most powerful shot.

Goal: Any time the ball crosses, at any height, the line between the goal posts, it is considered a goal regardless of who knocks it through, including the pony.

Handicap: All players are rated on a scale of -2 to 10 (the higher the better). Although the word 'goal' is often used after the rating, it bears no relation to the number of goals a player scores in a match, but to his overall playing ability. A player's horsemanship, range of strokes, speed of play, team and game sense are the factors considered in determining his handicap. The team handicap is the sum of its players' handicaps.

In handicap matches of six chukkas, the team with the lower handicap is awarded the difference in goals at the start of the game. For example, a 26-goal team would give two goals start to a 24-goal team.

For matches other than six chukkas, the side with the lower handicap starts with a number of goals start according to the following formula. The difference in the teams handicaps is multiplied by the number of chukkas to be played and then divided by six. Fractions count as half a goal. For example, a 26 goal team would give a 24 goal team 11/2 goals start in a four chukka match.

Hook: Provided the player is on the same side of the opponent's pony as the ball, he may spoil the opponent's shot by putting his stick in the way of the striking player's. 

HPA: Hurlingham Polo Association. The governing body of polo in the UK. http://www.hpa-polo.co.uk.

Intervals: Three- minutes long rest periods between chukkas. Half time is five minutes.

Judges: Goal judges are positioned behind each goal to signal whether a goal has been scored. Hard hats are worn for protection. Alo known as flagmen.

Knock-in: Should a team hit the ball across the opponent's backline during an attack, the defending team resumes the game with a free hit from the backline where the ball went over. It is equivalent to a goal kick in soccer. 

Leave it:  To ride past the ball so that the teammate behind can hit it. 

Line of the Ball: 'Crossing the line' is the most frequent foul in polo. The line of the ball, namely the imaginary line along which the ball travels, represents a right of way for the player following nearest that line. There are strict rules governing opponents entry in to the right of way. In the picture below the green line represents the line of the ball, the player on the red line is fouling because they crossed the line.