monocompound
/ˈmɒnə(ʊ)ˌkɒmpaʊnd/noun
1 Chemistry. In inorganic chemistry: a compound, especially a binary compound, whose molecule contains one atom of a specified element. In organic chemistry: a derivative whose molecule contains only a single substituted group or radical.
2 Pharmacology. A pharmaceutical drug used alone, as in monotherapy.
Origin
Mid 19th century; earliest use found in Henry Watts (1815–1884), chemist. From mono- + compound.