The word oftenness refers to the frequency of an occurrence or action. However, there are several synonyms that can be used instead of oftenness depending on the context. The word frequency is a common synonym that is often used in scientific or statistical contexts. Repeatedness, recurrence, and regularity are also synonyms that can be used to describe the frequency of something. If the context is related to a high frequency, words like frequent, constant, and consistent can be used instead of oftenness. On the other hand, words like rareness, infrequency, and sporadic can be used to describe the opposite i.e., low frequency.