epi- prefix. 
['ɛpi] Usu. ep- 
[ɛp, unstressed ɪp] before an unaspirated vowel, eph- 
[ɛf, unstressed ɪf] before an aspirated one.
[Repr. Greek 
epi on, near to, above, in addition.]
1. Occurring, esp. in scientific words, with the senses 'on', as 
epicycle, 
epigraph, 'above, overlying', as 
epicotyl, 
epidermis, 'near to', as 
epipubis, 'in addition', as 
epiphenomenon.
2. 
Chemistry, 
Mineralogy, & 
Geology. In names of substances, denoting 
(a) analogy or similarity of composition, 
(b) a bridge in a molecule.
 ■   epi'calyx 
noun, pl. -yces 
[-ɪsi:z], -yxes, 
Botany a whorl of small bracts like sepals surrounding the true calyx in certain plants, esp. members of the mallow family 
L19. ■   epicarp 
noun (
Botany) the outermost layer of the pericarp in a fleshy fruit; the peel, the skin: 
E19. ■   epichile 
[-kʌɪl] noun [Greek kheilos lip] Botany the flat projecting outer part of the hinged labellum found in some orchids 
M19. ■   epichlor'hydrin 
noun Chemistry a cyclic epoxide, C
3H
5OCl, that is a toxic flammable volatile liquid used esp. in the manufacture of epoxy resins 
M19. ■   epi'chordal 
adjective (
Zoology) situated or occurring on the dorsal side of the notochord 
L19. ■   epi'clastic 
adjective (
Geology) (of rock) formed on the earth's surface by the alteration of pre-existing rocks 
L19. ■   epi'cormic 
adjective (
Botany) 
[Greek kormos trunk (of a tree)] (of a shoot or branch) growing from a previously dormant bud on the trunk or a limb of a tree 
E20. ■   epicotyl 
[-'kɒtɪl] noun (
Botany) the part of an embryo or seedling stem above the cotyledon(s) 
L19. ■   [-ɪǝ], 
Botany the surface layer of the fruiting body in certain lichens and fungi 
L19. ■   epitope noun [Greek topos place] Medicine the part of an antigen molecule to which an antibody molecule attaches itself 
M20. ■   epi'topic adjective (
Medicine) of or pertaining to an epitope 
M20. ■   epi'trochlear adjective (
Anatomy) situated above or near the trochlea of the elbow-joint 
M20. ■   epizone noun (
Geology) a metamorphic zone characterized by moderate temperature, low pressure, and high stress 
M20.  [TahlilGaran] English Dictionary ▲