OPERATIONS RESEARCH

\ˌɒpəɹˈe͡ɪʃənz ɹɪsˈɜːt͡ʃ], \ˌɒpəɹˈe‍ɪʃənz ɹɪsˈɜːt‍ʃ], \ˌɒ_p_ə_ɹ_ˈeɪ_ʃ_ə_n_z ɹ_ɪ_s_ˈɜː_tʃ]\
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2006 - WordNet 3.0
By Princeton University
 
2011 - English Dictionary Database
By DataStellar Co., Ltd
 
2010 - Medical Dictionary Database
By DataStellar Co., Ltd