Antonyms for the word "obligatoriness", which refers to the state of being mandatory or required, could include words like "noncompulsory", "optional", "voluntary", or "discretionary". A situation or action that is not necessary or mandatory can be described as "elective" or "freewill". Other antonyms for obligatoriness could be "discretion" or "volition", which refer to having the power or right to make a choice or decision. In some contexts, synonyms for obigatoriness might include "exemption" or "dispensation", which refer to the state of being exempt from a rule or obligation. Overall, there are a variety of terms that can be used to describe the absence of obligatoriness, depending on the context and specific meaning desired.