Voluntary is pronounced VOL-ən-ter-ee (IPA /ˈvɑːlənˌtɛri/). Stress 'VOL' at the start — 'VOL-un-ter-ee'.
IPA: /ˈvɑːlənˌtɛri/
Syllables: VOL · ən · ter · ee
Common ESL mistake: Learners stress the middle saying 'vol-UN-tary'.
Tip: Stress 'VOL' at the start — 'VOL-un-ter-ee'.