Duration: A game of rugby consists of two halves of 40 minutes with injury time added on at the end of each half. This is not as long as you might expect, because physiotherapists are often allowed onto the pitch while play continues.
Players: Each side consists of 15 players, divided into eight forwards and seven backs. A total of seven substitutes are allowed for international matches. (There are also seven and 10-man versions of rugby union, played almost exclusively at tournaments.)
Officials: There is one referee assisted by two touch judges, who mark where the ball goes out of play, adjudge kicks at goal and inform the referee of foul play.
A fourth official controls replacements and substitutes. There is also a video referee in International and televised rugby matches.
The object of the game is to score more points than your opponents. There are a number of ways to achieve this.
Try: A try is worth five points. It is scored when a player places the ball on the ground with downward pressure in the in-goal area between the try line and dead ball line of the opposition's half.
Tries can be scored in a number of ways, other than running over the try line and putting the ball down.
They include the pushover try, scored by driving the opposition's scrum back over its own line; the momentum try, where a player slides into the in-goal area; and the penalty try, awarded when a team illegally obstructs the opposition to prevent a certain try from being scored.
There is no such thing as an "own try". If you touch the ball down in your own in-goal area, it results in a kick or a scrum.
Conversion: If a team scores a try, they have an opportunity to "convert" it for two further points by kicking the ball between the posts and above the crossbar - that is, through the goal. The kick is taken from a point level with where the try was scored.
Penalty kick: If a side commits a serious offence, a penalty is awarded and the opposition can take the option of a place kick at goal from where the infringement occurred. If successful, it is worth three points.
Drop goal: A drop goal for three points is scored when a player kicks the ball from hand through the opposition's goal. But the ball must touch the ground between being dropped and kicked.
Passing: All passes in rugby must travel backwards. There are different varieties of pass, including the flat, direct spin pass; the short, close-quarters pop pass; and the floated pass - a long pass which an advancing player can run onto at pace.
Kicking: Kicking forms a major part of rugby and is used to start and restart the game, score points, win territory, launch an attack or get a team out of trouble (known as a clearance kick).
If the ball is kicked directly into touch by a player from behind his own 22m line, the resulting lineout is taken where the ball crossed the touchline.
But if he is outside his 22, the lineout is taken level with the place from where the ball was kicked (except in the case of penalties).
Players must be behind the kicker for all set piece kicks, such as kick-offs. But if a kick is made in loose play, then players can be in front of the kicker, although they must not advance towards where the ball is going to land until the kicker has put them onside by getting in front of them.
Players use a wide range of kicks, such as the high, hanging up-and-under/garryowen/bomb; the end-over-end grubber kick; or the speculative chip-and-chase.