3 syllables:
regular, tegular

5 syllables:
extraregular

6 syllables:
stereoregular

7 syllables:
regular-irregular

3 syllables:
editor, decolor, semaphore, sepulcher, nebular, hellebore, delaware, belshazzar, predator, headhunter, ecuador, creditor, metaphor, guenevere, specular, senator, messenger, settler, metamere, secretaire, escolar, leveller, debugger, elater, prelature, seminar, stepmother, sepulture, reckoner, megathere, reservoir, cellular, tetraspore, questioner, wrestler, seconder, sepulchre, pedaler, medicare, megaspore, premolar, belabour, presenter, temperature, pensioner, reveler, stepbrother, stegosaur, secular, eleanor, endospore, engler, escobar, genitor, jennifer, leicestershire, leveler, meddler, mevacor, pedaller, reveller, second-year, sevener, strengthener

4 syllables:
emmentaler, centromere, confectioner, noncellular, executor, dosemeter, expenditure, developer, molecular, acellular, misdemeanour, investiture, corregidor, text editor, room temperature, embezzler, competitor, ctenophore, art editor, asthenosphere, concessioner, congenator, cross-questioner, dead metaphor, high temperature, low temperature, sports editor, state senator, subeditor, vulpecular

5 syllables:
body temperature, intracellular, primogenitor, extracellular, curie temperature, city editor, copy editor, linkage editor, business editor, divine messenger, drunken reveler, frozen metaphor

6 syllables:
managing editor, differentiator, absolute temperature, newspaper editor

7 syllables:
capital expenditure, capital of delaware, capital of ecuador