Definition from Wiktionary, the free dictionary
- When combined with a term beginning with a consonant, end- concatenates with the interfix -o- (as endo-).
- The prefix end- is usually stressed in the terms it forms (as in endoscope: ĕnʹdōskōp); however, it is never stressed when stress falls on the following syllable (as in endoscopy: ĕndŏʹskŏpi), and stressing the prefix is optional when the subsequent syllable is stressed (as in endoscopic: ĕndōskŏʹpĭk or ĕn'dōskŏʹpĭk).
internal, within, inside
terms ultimately deriving from ἔνδον (endon, “within”), but not formed with this prefix