Meaning of -ARY in English
-ary BrE AmE ə ri, eri —In words of three syllables this suffix is usually weak, ər i ( ˈ binary, ˈ glossary). In longer words it is usually weak in British English, ər i (frequently reduced to ri ); but strong in American English, er i : thus ˈ arbitrary ˈɑːb ɪtr ər i AmE \ ˈɑːrb ə trer i, ˈ customary ˈkʌst əm ə r‿i ‖ ˈkʌst ə mer i . The stress may fall either one or two syllables further back (ex ˈ emplary, ˌ anni ˈ versary; ˈ mercenary, ˌ inter ˈ planetary). A few words differ in stress as between British English and American English (co ˈ rollary ‖ ˈ corollary).
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012