"existing or continuing for ten years; occurring every ten years," 1650s, with -al (1) + Latin decennium, from decennis "of 10 years," from decem "ten" (from PIE root *dekm- "ten") + annus "year" (see annual (adj.)). For vowel change, see biennial. As a noun, "a tenth anniversary," by 1884.

word-forming element in words of Greek origin or formation meaning "five, containing five," from Greek penta- (before a vowel pent-), combining form of pente "five," related to Aeolian pempte (from PIE root *penkwe- "five"), with -a- probably by analogy of hepta-, ennea-, deka-.

word-forming element, from Greek -oma, with -o-, lengthened stem vowel + -ma, suffix forming neuter nouns and nouns that indicate result of verbal action (equivalent of Latin -men); especially taken in medical use as "morbid growth, tumor," based on sarcoma, carcinoma.

late 14c., "spoken, oral," from Old French vocal (13c.), from Latin vocalis "sounding, sonorous, speaking," as a noun, "a vowel," from vox (genitive vocis) "voice" (from PIE root *wekw- "to speak"). In reference to music (as opposed to instrumental), first recorded 1580s; meaning "outspoken" first attested 1871. Vocal cords is from 1872; see cord.

"a striking or cutting off," especially "the cutting off or suppression of a letter, sound, or syllable in speaking or writing," 1580s, from Latin elisionem (nominative elisio) "a striking out, a pressing out," in grammar, "the suppression of a vowel," noun of action from past-participle stem of elidere (see elide).