Conscientious is pronounced kon-shee-EN-shəs (IPA /ˌkɑːnʃiˈɛnʃəs/). The 'sci' becomes 'shee'; stress 'EN' in the middle.
IPA: /ˌkɑːnʃiˈɛnʃəs/
Syllables: kon · shee · EN · shəs
Common ESL mistake: Learners pronounce 'sci' as /sai/ saying 'kon-sigh-EN-shus'.
Tip: The 'sci' becomes 'shee'; stress 'EN' in the middle.