A "disabled person" is defined by the Disability Discrimination Act 1995 as someone with "a physical or mental impairment which has a substantial and long-term adverse effect on his ability to carry out normal day to day activities" (DDA 1995 s.1). The Act expands on what this means. Persons who have had a disability but have since recovered are expressly included. Progressive conditions (eg cancer) are also expressly covered.

Until December 2005 a mental impairment had to result from or consist of a clinically well-recognised illness to count as a disability for DDA purposes but that requirement was then removed. The Disability Discrimination Act 2005 made this and other changes to the DDA definition of disability with effect from 5th December 2005. For example that Act also widened the definition to benefit those with HIV, Aids, cancer and multiple sclerosis (MS) (see notes at Acts of Parliament etc/Disability Discrimination Act 2005 ).

Changes in the law relating to discrimination, mainly of a technical nature but including in particular disability discrimination, are in effect from 1st October 2010 under the Equality Act 2010 (see notes at Acts of Parliament etc/Equality Act 2010 ).

There is important Official Guidance on "matters to be taken into account in determining questions relating to the definition of disability". A new version is in effect from 1st May 2006. Like the Disability Discrimination Act Employment Code of Practice (see Disability Discrimination/Disability Discrimination Act 1995/Code of Practice ) the Guidance does not have the force of law but Courts and Tribunals are obliged to take it into account (DDA 1995 s.3(3) and see Virdi v Commissioner of Police of the Metropolis (2) EAT 2006 on 18th October 2006).

New Official Guidance under the Equality Act is expected to come into force on 1st May 2011 (see Hansard HC 10th Feb 2011, col 16WS)

See also Disability Discrimination/Disability Discrimination Act 1995/recent cases .