The 2008 Paralympics in Beijing involves 20 sports but not all disability categories can compete in each event.
Each sport has different physical demands and so has its own set of classifications.
Archery is open to athletes with a physical disability and classification is broken up into three classes:
Archery is divided into sitting, standing and wheelchair athletes
ARW1: spinal cord and cerebral palsy athletes with impairment in all four limbs
ARW2: wheelchair users with full arm function
ARST (standing): athletes who have no disabilities in their arms but who have some disability in their legs. This group also includes amputees, les autres and cerebral palsy standing athletes
Some athletes in the standing group will sit on a high stool for support but will still have their feet touching the ground.
All disability groups can compete in athletics but a system of letters and numbers is used to distinguish between them.
A letter F is for field athletes, T represents those who compete on the track, and the number shown refers to their disability.
11-13: track and field athletes who are visually impaired
20: track and field athletes who are intellectually disabled
31-38: track and field athletes with cerebral palsy
41-46: track and field amputees and les autres
T 51-56: wheelchair track athletes
F 51-58: wheelchair field athletes
Blind athletes compete in class 11 and are permitted to run with a sighted guide, while field athletes in the class are allowed the use of acoustic signals, for example electronic noises, clapping or voices, if they compete in the 100m, long jump or triple jump.
Athletes in classes 42, 43 and 44 must wear a prosthesis while competing, but this is optional for classes 45 and 46.
Boccia (a bowling game) is open to athletes with cerebral palsy and other severe physical disabilities (eg, muscular dystrophy) who compete from a wheelchair, with classification split into four classes.
BC1: Athletes may compete with the help of an assistant, who must remain outside the athlete's playing box. The assistant can only stabilize or adjust the playing chair and give a ball to the player on his request
BC2: Athletes have poor functional strength in their extremities, but can propel a wheelchair and are not eligible for assistance
BC3: For players with a very severe physical disability. Players use an assistive device and may be assisted by a person, who will remain in the player's box but who must keep his/her back to the court and eyes averted from play
BC4: For players with other severe physical disabilities - not necessarily cerebral palsy. Players are not eligible for assistance
Cycling is open to amputees, les autres, athletes with cerebral palsy and visually impaired athletes, competing in individual road race and track events.
Athletes with cerebral palsy are split into four divisions according to the level of their disability, where class four comprises the more physically able.
Visually impaired athletes compete together with no separate classification system. They ride in tandem with a sighted guide.
Amputee, spinal cord injury and les autres competitors compete within these groups:
LC1: Riders with upper limb disabilities
LC2: Riders with impairment in one leg but who can pedal normally
LC3: Riders with impairment in one lower limb who will usually pedal with one leg only
LC4: Riders with disabilities affecting both legs
Athletes with more severe disabilities take part in handcycling, which is now included in the cycling programme.
Handcyclists compete in the following disability divisions:
HCA: For athletes with complete loss of trunk and lower limb function
HCB: For athletes with complete loss of lower limb function and limited trunk stability
HCC: For athletes with complete loss of lower limb function but few other functional disabilities, or for athletes with partial loss of lower limb function combined with other disabilities which mean conventional cycling is not viable
All disability groups can take part in equestrian sport but riders are divided into four grades.
Equestrian competitors are graded according to ability
Grade 1: Severely disabled riders with cerebral palsy, les autres and spinal cord injury
Grade 2: Athletes with reasonable balance and abdominal control including amputees
Grade 3: Athletes with good balance, leg movement and coordination including blind athletes
Grade 4: Ambulant athletes (those able to walk independently) with either impaired vision or impaired arm or leg function
Five-a-side football is played by those with a visual impairment, while seven-a-side football is played by athletes with cerebral palsy.
People who take part in five-a-side blind football are classified, according to their level of sight, as B1, B2 or B3.
Players in the B1 classification are considered blind (while those rated B2 and B3 are classified as visually impaired or partially sighted).
Outfield players are B1, but must wear eye-patches and blindfolds. The goalkeeper is sighted, but cannot leave the area. There are no offside rules.
The football contains ball bearings to produce a noise when it moves.
Seven-a-side football consists of players from the C5, C6, C7 and C8 divisions, rated according to limb control and co-ordination problems when running.
All classes are comprised of ambulant athletes, where those in class five are least physically able through to class eight who are minimally affected.
At least one C5 or C6 class athlete per team must play throughout the match. If this is not possible, the team must play with six players. Furthermore, no more than three players from category C8 are allowed to play at the same time.
Outside the Paralympics, football is also played by athletes from three other disability groups (deaf, amputees or those footballers who have a learning difficulty).
Goalball is played by visually impaired athletes and a special rule means there is no need for classification.
Participants wear "black out" masks to ensure everyone competes equally.
Judo is contested by visually impaired athletes only. There is no categorisation as competitors are divided by weight in the same way as able-bodied athletes.
The only sign that judo at the Paralympics is different from other top level judo events is the varied textures of the mat, indicating the competition area and zones.
Male athletes who are blind or have a visual impairment compete for the gold medal, and the competition rules follow those of the International Judo Federation.
Powerlifting is open to all athletes with a physical disability and is classified by weight alone.
Powerlifting is organised by weight not disability
Powerlifters competing at the Paralympics have disabilities including paralysis, cerebral palsy and lower limb amputation.
Both male and female competitors take part in 10 weight classes.
Rowing, new for the 2008 Paralympic programme, is divided into four boat classes.
LTA4+: A four-person, mixed gender, sweep-oar boat plus cox with sliding seats. Open to athletes with an impairment but who have movement in the legs, trunk and arms. A boat can include a maximum of two visually impaired athletes.
TA2x: A two-person, mixed-gender scull for athletes with trunk and arm movement only.
AM1x: A fixed-seat single scull boat for men. Athletes have full movement in their arms only.
AW1x: A fixed-seat single scull boat for women. Athletes have full movement in their arms only.
Sailing is a multi-disability sport where athletes from the amputee, cerebral palsy, visually impaired, wheelchair and les autres groups can compete together.
There are three sailing classes: the Sonar, which is a mixed three-person crew, the SKUD18, a new two-person class introduced for Beijing, and the 2.4mR event, which is single-crewed.
Competitors are ranked according to a points system where low points are given to the severely disabled and high points for the less disabled.
Each crew of three is allowed a maximum of 12 points between them.
Single-handed sailors must have a minimum level of disability which prevents them competing on equal terms with able-bodied sailors.
Shooters are divided into wheelchair and standing groups.
These divisions are split into six sub-classes, each of which determines the type of mobility equipment the competitor is allowed to use.
SH1: For pistol and rifle competitors who do not require a shooting stand
SH2: For rifle competitors who have an upper limb disability and require a shooting stand
Swimming is the only sport that combines the conditions of limb loss, cerebral palsy (coordination and movement restrictions), spinal cord injury (weakness or paralysis involving any combination of the limbs) and other disabilities (such as Dwarfism and major joint restriction conditions) across classes.
Britain's Jim Anderson won four swimming golds in Athens
1-10: Allocated to swimmers with a physical disability
11-13: Allocated to swimmers with a visual impairment
14: Allocated to swimmers with an intellectual disability
The prefix S denotes the class for freestyle, backstroke and butterfly. SB denotes the class for breaststroke, and SM denotes the class for individual medley.
The prefix and class number provide a range of classifications, from swimmers with severe disability (S1, SB1, SM1) to those with minimal disability (S10, SB9, SM10).
In any one class swimmers may start with a dive, or in the water. This is taken into account when classifying an athlete.
Swimmers may have a classification which varies according to their event - for example, it may change between breaststroke and backstroke, according to the effect of their disability on the event in question.
Class 14 has been suspended for the Athens and Beijing Games.
Table tennis is played by athletes with a physical or intellectual disability spread over 11 classes.
1-5: Athletes competing from a wheelchair, with class one the most severely disabled and class five the least disabled
6-10: Ambulant athletes, with class six the most severely disabled and class 10 the least
11: Athletes with an intellectual disability (suspended for the Athens and Beijing Games)
Volleyball is contested by athletes with a physical disability and has both a sitting and standing event.
In sitting volleyball the court is smaller than standard and has a lower net. Games are contested by athletes with a minimal disability that prevents them from competing with able-bodied athletes.
Standing volleyball uses a full-sized court and normal height net, and is played by athletes split into three classes according to their disabilities.
Basketball is open to wheelchair athletes, whose impairments may include paraplegia, lower limb amputation, cerebral palsy and polio.
Athletes are classified according to physical ability and are given a points rating between 1 and 4.5. One point equates to the most severe disability, 4.5 to the least.
Each team fields five players but may not exceed a total of 14 points at any given time.
Fencing is open to wheelchair athletes, whose impairments may include spinal cord injuries, lower limb amputation and cerebral palsy.
Athletes competing in this event are split into two classes.
A: Athletes with good balance and recovery, and full trunk movement.
B: Athletes with poor balance and recovery, but full use of one or both upper limbs.
Wheelchair rugby athletes are classified using a points system, with the most severely disabled athletes being graded at 0.5 points, rising to 3.5 points for the more able.
Wheelchair rugby is played by two teams of four on a basketball court
Each team is comprised of four players and is allowed a maximum of eight points on court at any one time.
Tennis is played from a wheelchair with two classes - open and quad (disability in all four limbs).
In wheelchair tennis competitions, players are allowed two bounces of the ball, the first bounce being within the bounds of the court.