dehydr-
combining form 
or dehydro-
Etymology: International Scientific Vocabulary, from de- + hydr- 
1. : dehydrated 
< dehydromucic acid C4H2O(COOH)2 >
2. : dehydrogenated 
< dehydroabietic acid C19H27COOH >
or dehydro-
1.
< dehydromucic acid C4H2O(COOH)2 >
2.
< dehydroabietic acid C19H27COOH >