The German law generally uses metrics and criteria for determining whether disability exists that are different from those used in the US and UK. Thus, the scope of the concept will be naturally different. However, the purpose behind the concept (protect and compensate disabled persons out of a communal sense of fairness) and the effect thereof (providing those persons with support) are fundamentally the same.
There are multiple definitions - click on the translation that matches your context.
an illness, injury, or condition that makes it difficult for someone to do the things that other people do
A £6m centre for people with learning disabilities has been opened on South Tyneside.
a disadvantage or handicap, particularly one imposed or recognized by the law
The suspension of his driving license, a major civil disability in his profession, resulted from his conviction for driving under the influence of alcohol.