Printable Version
Pronunciation: pi-ree-ah-dik Hear it!

Part of Speech: Adjective

Meaning: 1. Occurring at regular intervals. 2. Occurring from time to time. 3. (Chemistry) Referring to a tabular arrangement of atomic numbers.

Notes: A recent discussion of the difference in the meanings of periodic, timely, and regular raised the question of how to use them. Timely means "happening at the appropriate time" and regular means "arranged with equal space between events or objects". We may extend today's word by the semantically empty suffix -al, which is obligatory before the adverb suffix -ly: periodically. The quality of being periodic is called periodicity.

In Play: Today's word may refer to events that are equally spaced: "Renting hotel rooms on an weekly basis is an example of periodic occupancy." It may also used for events that are regular, but not equally spaced: "Everyone should have periodic contact with national news."

Word History: This word was borrowed from French periodique, which inherited it from a Latin (periodicus) borrowing from Greek periodikos. The Greek word is the adjective for periodos "cycle, period of time". Periodos was once a compound comprising peri "around" + hodos "going", a word related to Russian khodit' "to go/come". Peri goes back to PIE per "over, through", which also shows up in Latin per "through", Lithuanian per "over, across, through", and English for. Some derive the Greek and Russian words from PIE sod- "course", traditionally connected with Russian khod "course, progress", though the Greek and Russian words might have just been borrowed from Iranian. (Today's thorny Good Word was suggested by David Myer, who periodically suggests equally good ones.)

Dr. Goodword,

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