English Reference
adjective

periodic

adj.
US /ˌpɪɹiˈɑdɪk/ pe·ri·od·ic

  1. 01 B2 Upper Intermediate

    happening again and again at regular times.

    occurring or appearing at regular intervals of time.

    Simple

    The machine requires periodic maintenance to keep it running smoothly.

    In context

    The company conducts periodic reviews of its safety protocols to ensure they remain compliant with the latest industry regulations.

  2. 02 C1 Advanced Technical Science

    having a pattern that repeats itself exactly over time.

    having a structure or behavior characterized by repeated cycles or periods.

    Simple

    The ocean tides are a periodic movement caused by the moon.

    In context

    The researcher observed a periodic fluctuation in the data, suggesting that the chemical reaction followed a predictable cycle every four hours.

    aperiodic
  3. 03 C2 Proficiency Technical Astronomy

    relating to the time it takes for a planet or moon to complete one circle.

    pertaining to the time taken for a celestial object to complete one full revolution in its orbit.

    Simple

    Comets have periodic orbits that bring them near Earth every few decades.

    In context

    The periodic motion of the planets was first accurately described using elliptical models rather than perfect circles.

  4. 04 C2 Proficiency Technical Science

    relating to a specific type of acid that contains iodine.

    relating to or derived from an acid of iodine in its highest oxidation state.

    Simple

    The teacher explained how periodic acid is used in some laboratory tests.

    In context

    The technician prepared a solution of periodic acid to act as an oxidizing agent in the histological staining process.

    Usage

    Pronounced /ˌpɜːraɪˈɒdɪk/ (per-iodic) unlike the common word /ˌpɪəriˈɒdɪk/.

They received periodic health education along with broad lifestyle recommendations.

ScienceDaily· 6 Sept 2026

If a structure is periodic, researchers can analyze only a small portion of it and predict the behavior of the entire device.

Phys.org· 4 Sept 2026

Etymology 1

From French périodique, from Medieval Latin periodicus (“cyclical”), from Latin periodus (“complete sentence, period, circuit”), from Ancient Greek περίοδος (períodos, “cycle, period of time”). By surface analysis, period + -ic.

Etymology 2

From per- + iodic.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Ancient Greek περίοδος
Level B2 · Upper Intermediate
Frequency Frequent
Updated