Ma'anar ƙamus na kalmar "haɗin kai" shine tsarin aiki tare da wasu don manufa ɗaya ko fa'ida. Ya ƙunshi haɗin kai, raba albarkatu, da sadarwa yadda ya kamata don cimma manufa ko manufa ɗaya. Haɗin kai na iya faruwa tsakanin daidaikun mutane, ƙungiyoyi, ko ma ƙasashe, kuma galibi ana ganin su a matsayin babban jigon haɗin gwiwa da haɗin gwiwa mai nasara. Yana buƙatar yarda don sasantawa da fahimtar ƙimar aiki tare don cimma manufa ɗaya.