Another use of the term “ordinary” in Catholic liturgical parlance is to identify prayers that are always included in the liturgy, as opposed to the “propers”, which are prayers specific to a particular day. With very few exceptions, all these prayers have prescribed texts, translated from the official Latin text.
In the current Roman missal, most of the ordinary prayers have several options, and the priest who is celebrating mass may select which option will be used.
Were you aware that there were some prayers that were always used, and some that were specific to the day? What do you think about that?