rationale
noun [ C, usually singular ]
uk/ˌræʃəˈnɑːl/ us/ˌræʃəˈnæl/the set of reasons that are given to explain a particular decision, action, etc.:
We have spoken to shareholders to explain the rationale behind our bid.
the rationale for sth/doing sth This data can be abused by insurance companies seeking any rationale for charging higher rates.