2 syllables:
essens, lessens, lessons, basins, chasen's, chastens, hastens, jason's, jasons, kastens, leysen's, mason's, masons

3 syllables:
marcescens, mckesson's, freemasons, stonemasons, unfastens, washbasins

4 syllables:
mumford & sons, vasopressins, diapasons

5 syllables:
delicatessens, cytochalasins

2 syllables:
sessions, heavens, nations, sevens, stations, avens, evans, heaven's, stephens, asians, haitians, havens, nation's, nations'

3 syllables:
impressions, foundations, relations, occasions, concessions, confessions, expressions, possessions, professions, recessions, creations, croatians, donations, frustrations, locations, notations, plantations, temptations, vacations, vibrations

4 syllables:
quarter sessions, regulations, operations, law of nations, declarations, fluctuations, expectations, generations, applications, accusations, allegations, appalachians, aspirations, booster stations, calculations, celebrations, combinations, complications, concentrations, confrontations, congregations, consultations, conversations, corporations, decorations, delegations, demonstrations, deportations, destinations, explanations, implications, indications, innovations, installations, invitations, limitations, medications, motivations, nominations, obligations, observations, occupations, populations, preparations, presentations, publications, relay stations, reparations, reputations, reservations, revelations, sarajevans, situations, vaccinations, variations, violations

5 syllables:
public relations, communications, united nations, congratulations, organizations, worldly possessions, accommodations, administration's, administrations, appropriations, assassinations, association's, associations, civilizations, considerations, deliberations, determinations, evacuations, evaluations, examinations, genus impatiens, immunizations, interpretations, investigations, modifications, negotiations, organization's, qualifications, ramifications, recommendations, representations

6 syllables:
comity of nations, commonwealth of nations, base of operations, trading operations

7 syllables:
telecommunications, statute of limitations, chemical operations, treasury obligations

8 syllables:
calculus of variations, riot control operations

9 syllables:
alternation of generations, diplomatic negotiations

18 syllables:
food and agriculture organization of the united nations