The two became friends and checked in periodically by telephone.
I happen to find male melancholy endlessly fascinating (being male, and periodically melancholy), but does everyone?
Second funniest, midwife asked me to rate my pain 1-10 periodically and at one point I said 9.
1640s, from French périodique (14c.), from Latin periodicus, from periodus (see period).
Periodic table in chemistry (1889) is from notion of the arrangement, in which similar properties recur at intervals in elements in the same area as you read down the rows of the table. This sense of the word is attested from 1872 (periodic law).
periodic pe·ri·od·ic (pĭr'ē-ŏd'ĭk)
Having or marked by repeated cycles.
Recurring at regular intervals.