for which any return to it may occur at irregular times; not periodic.
That does not have a periodic vibration
That does not recur periodically
Periodic.
Published at regular intervals of more than one day, especially weekly, monthly, or quarterly.
Of, or relating to such a publication.
A regularly issued thematic publication that contains the most current information in its field, often the primary means for communication of original scholarship or creative work at the cutting edge of research in its field.
A publication issued regularly, but less frequently than daily.