Term used mainly in the German literature for starting material (reactant). It should
be avoided in English, because there it means '
something that comes out' and not '
something that goes in'. The German use of the term is in fact also incorrect.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1108