This English term is just as vague and indefinite as its German counterpart, "Arbeitsunfaehigkeit". In the United States, the term connotes a more serious and long-lasting handicap. Since the German concept often applies to less permanent situation - the employee is rendered unable to work for a certain period of time - we would suggest caution when using disability as a translation for Arbeitsunfaehigkeit. Both terms convey the notion of incapacity, but the scale of that incapacity and the effects of being classified as one or the other can be quite different.
There are multiple definitions - click on the translation that matches your context.
severe disability means:
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.