in·o·sine 
(ĭnə-sēn′, -sĭn, īnə-)
(ĭnə-sēn′, -sĭn, īnə-)n.
A nucleoside that is involved in purine metabolism, as a precursor and a metabolite of adenosine.
[Greek īs, īn-, sinew; see wei- in the Appendix of Indo-European roots + -OS(E)2 + -INE2.]