The 2004 Paralympics in Athens will stage 19 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
W1: spinal cord and cerebral palsy athletes with impairment in all four limbs.
W2: wheelchair users with full arm function
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 are used to distinguish between them.
A letter F is for field athletes, T determines those who compete on the track while the number 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
Boccia (a bowling game) is open to athletes with cerebral palsy who compete from a wheelchair and classification is split into four classes.
This classification is quite complex but in simple terms athletes are split into two basic categories.
1: Those athletes who are dependent on an electric wheelchair or assistance for mobility.
2: Those with poor functional strength in all extremities and trunk but able to propel a wheelchair.
Cycling is open to amputees, les autres, cerebral palsy and visually impaired athletes who compete 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 the specific groups:
LC1: Riders with upper limb disabilities
LC2: Riders with disabilities in one leg but who can pedal normally
LC3: Riders with a handicap 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 hand cycling and this is now included in the cycling programme.
Competitors who normally require a wheelchair for general mobility or who cannot use a normal bicycle are split into three classes, HCA, HCB and HCC.
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 (able to walk independently) athletes with either impaired vision or impaired arm or leg function.
Football is split into two diisabilities Blind and Cerebral Palsy.
People who take part in 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).
There are five players in each team
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 so that it makes a noise when it moves
Football (not played in the Paralympics) is also played by athletecs with three other disabilities (deaf, amputees or those footballers who have a learning difficulty)
The Cerebral Palsy classification is split into classes five to eight but each team must include at least one member from either class five or six.
All classes are comprised of ambulant athletes, where those in class five are least physically able through to class eight who are minimally affected.
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 and again there is no categorisation as competitors are divided by weight in the same way as able-bodied athletes.
Powerlifting is organised by weight not disability
The only signs that the judo competitions at the Paralympic Games are different from other top level judo events are the varied textures on the mats indicating competition area and zones.
The same high calibre of competition as in all other international judo events is immediately evident at the Paralympics.
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 like judo classification is done by weight alone.
Both male and female competitors take part in 10 weightclasses.
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 two sailing classes: the Sonar, which is a mixed three-person crew 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 less disabled.
Each crew of three is allowed a maximum of 12 points between them.
Single-handed sailors must have at least a minimum level of disability which prevents them from competing on equal terms with able bodied sailors.
Shooters are divided into wheelchair and standing groups but these divisions are then split into six sub-classes, each of which will determine the type of mobility equipment the competitor is allowed to use.
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 (little people); major joint restriction conditions) across classes.
Classes 1-10 are allocated to swimmers with a physical disability
Classes 11-13 are allocated to swimmers with a visual impairment
Class 14 is allocated to swimmers with an intellectual disability
The prefix S denotes the class for Freestyle, Backstroke and Butterfly.
The prefix SB denotes the class for Breaststroke.
The prefix SM denotes the class for Individual Medley.
The range is from the swimmers with severe disability (S1, SB1, SM1) to those with the minimal disability (S10, SB9, SM10)
In any one class some swimmers may start with a dive or in the water and this is factored in when classifying the athlete.
Table tennis is played by athletes with a physical or with an intellectual disability spread over 11 classes.
1-5: Athletes competing from a wheelchair with class one being the most severely disabled and class five the least disabled.
6 -10: Ambulant athletes with class 6 the most severely disabled and class 10 the least.
11: Athletes with an intellectual disability.
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 and is contested by athletes with a minimal disability that prevents them from competing with able bodies athletes.
Standing volleyball uses a full sized court and normal height net and is played by athletes who are split into three classes according to their disabilities.
Basketball is open to wheelchair athletes.
Athletes are classified according to their physical ability and are given a points rating between 1-4.5: one pointers being the most severely disabled and 4.5 the least disabled.
Each team fields five players but may not exceed a total of 14 points at any given time.
Fencing is only open to wheelchair athletes who are split into three classes.
Class A: Athletes with good balance and recovery and full trunk movement.
Class B: Athletes with poor balance and recovery but full use of one or both upper limbs.
Class C: Athletes with severe physical impairment in all four limbs.
Athletes are classified on a points system similar to wheelchair basketball, with the most severely disabled athlete 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 8 points on court at any one time.
Tennis is played from a wheelchair with two classes - wheelchair and quadriplegic (disability in all four limbs).
The game follows traditional tennis rules and certainly maintains the same traditions of high levels of skill, fitness and strategy.
The only difference in wheelchair tennis competitions is that the players are allowed two bounces of the ball; the first bounce being within the bounds of the court.