Correct spelling for the English word "denidation" is [dˌɛnɪdˈe͡ɪʃən], [dˌɛnɪdˈeɪʃən], [d_ˌɛ_n_ɪ_d_ˈeɪ_ʃ_ə_n] (IPA phonetic alphabet).
The exfoliation of the superficial portion of the mucous membrane of the uterus; stripping off of the menstrual decidua.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.