The correct spelling of the word that refers to the act of acquiring something is actually "acquisition", not "assession". The correct pronunciation is [ˌæk.wɪˈzɪʃ.ən], with stress on the second syllable. The mistake may arise due to the similarity in sound between the "s" and "c", and the confusion between -ion and -sion word endings. However, it is important to strive for accurate spelling as it can impact the credibility of one's written communication.