# periodic

/ˌpɪɹiˈɑdɪk/ (US)

Source: https://englishreference.com/word/periodic
Updated: 2026-06-20

## Senses

### 1. at regular intervals

adjective · CEFR B2

happening again and again at regular times.

For teachers: occurring or appearing at regular intervals of time.

- The machine requires periodic maintenance to keep it running smoothly.
- The company conducts periodic reviews of its safety protocols to ensure they remain compliant with the latest industry regulations.

### 2. repeating cycles

adjective · CEFR C1 · Technical

having a pattern that repeats itself exactly over time.

For teachers: having a structure or behavior characterized by repeated cycles or periods.

- The ocean tides are a periodic movement caused by the moon.
- The researcher observed a periodic fluctuation in the data, suggesting that the chemical reaction followed a predictable cycle every four hours.

### 3. planetary orbits

adjective · CEFR C2 · Technical

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

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

- Comets have periodic orbits that bring them near Earth every few decades.
- The periodic motion of the planets was first accurately described using elliptical models rather than perfect circles.

### 4. chemical acid

adjective · CEFR C2 · Technical

relating to a specific type of acid that contains iodine.

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

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

## Examples

- The car needs periodic checks to stay safe.
- The satellite sends periodic signals back to Earth every six hours to confirm its location.
- While the market experiences daily fluctuations, economists look for periodic trends that repeat over several years to predict long-term growth.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.