Sc.D. or ScD is the abbreviation of the Latin Scientiae Doctor, which means "Doctor of Science". It is an academic doctoral degree on par with the wider known Ph.D. The Sc.D. is awarded predominantly in engineering sciences, whereas "classical" sciences seem to prefer the Ph.D. (Compare e.g.  and .)
The "Doctor of Science" is sometimes also abbreviated DSc or D.Sc. However, in the United Kingdom, the D.Sc. is a higher doctorate which is issued by a committee on the basis of a long research and publication record.