ra·tio·nale 
/ˌræʃəˈnæl/ noun
plural ra·tio·nales /ˌræʃəˈnæl/ noun [count] somewhat formal : the reason or explanation for something — usually singular ▪ That was a strange decision. What was their rationale? — often + for, behind, or of ▪ What was her rationale for leaving school? ▪ He explained the rationale behind his early retirement. ▪ I don't understand the rationale of his decision.
