composed primarily of bodily fluid material breast milk material ENVO bodily fluid classes differ from UBERON's treatment of bodily fluids. UBERON refers to the substance itself ("S"). We assert that UBERON's classes are the primary compositional component of the terms in ENVO ("S material"). Use of the ENVO terms is typically recommended when you wish to indicate that there may be other materials intermixed with S. A bodily fluid material which is composed primarily of breast milk, is a bodily fluid produced that is secreted from two milk-secreting glandular organs on a female's chest. milk