Definition

1. Adjective:
   • Recurring or reappearing from time to time: Describes something that happens repeatedly, though not necessarily with strict regularity, over a span of time.
   • Happening or recurring at regular intervals: Describes events or phenomena that occur in a predictable, cyclical pattern with consistent time gaps between occurrences.

Examples of Usage

• Adjective:
  • She experienced periodic feelings of anxiety before major presentations. (This describes the recurrence of a state over time.)
  • The periodic appearance of the seventeen-year locust is a fascinating natural phenomenon. (This describes an event recurring at a very long, regular interval.)
  • The company conducts periodic reviews of its safety protocols. (This describes reviews happening at set, regular times.)
  • The patient's symptoms were periodic, flaring up every few months. (This describes symptoms that come and go repeatedly.)

Advanced Usage

• In scientific contexts: "Periodic" often describes systems or functions with a precise, repeating cycle.
  • The scientist studied the periodic motion of the pendulum. (This refers to motion that repeats its path in equal intervals of time.)
• "Periodic table": A specific, fixed term in chemistry for the tabular arrangement of chemical elements ordered by atomic number, electron configuration, and recurring chemical properties, showing periodic trends.
  • Elements in the same column of the periodic table share similar chemical properties. (This is a proper noun for a specific scientific chart.)

Variants and Related Words

• Periodical (adjective & noun):
  • As an adjective, it is often synonymous with "periodic," meaning recurring at intervals.
  • As a noun, it refers to a magazine or journal published at regular intervals (e.g., weekly, monthly).

    • She subscribes to a monthly periodical about gardening.
• Periodicity (noun): The quality or character of being periodic; the tendency to recur at intervals.
  • The periodicity of the tides is influenced by the moon.

Synonyms

• Recurrent: Occurring again or repeatedly.
• Cyclical: Occurring in cycles; regularly repeated.
• Intermittent: Occurring at irregular intervals; not continuous or steady.
• Regular: Happening at uniform intervals of time.

Antonyms

• Continuous: Without interruption; unbroken.
• Sporadic: Occurring at irregular intervals or only in a few places; scattered or isolated.
• Aperiodic: Not periodic; irregular.

Related Phrases and Usage Notes

• Periodic function (Mathematics): A function that repeats its values at regular intervals.
  • The sine wave is a classic example of a periodic function.
• Periodic law (Chemistry): The principle that the properties of the chemical elements exhibit a periodic dependence on their atomic numbers.
• Usage Note: While "periodic" and "periodical" are often interchangeable as adjectives, "periodical" is the preferred term when referring to publications. "Periodic" is more commonly used in scientific and general contexts.

Adjective

1. recurring or reappearing from time to time
   • periodic feelings of anxiety
2. happening or recurring at regular intervals
   • the periodic appearance of the seventeen-year locust