# diurnal

/daɪˈɝnəɫ/ (US) · /dˈɪɜːnəl/ (UK) · CEFR C2 · Adjective

Source: https://englishreference.com/word/diurnal
Updated: 2026-06-22

## Definition

relating to the daily cycle of day and night. In plants, it describes leaves that open during the day and close at night.

For teachers: relating to the daily cycle of day and night; specifically, in botany, describing leaves that open during the day and close at night. Often used in technical contexts to describe plant movements or animal activity patterns.

## Examples

- The plant has diurnal leaves that open in the morning.
- Many desert plants have diurnal habits, opening their flowers only during the cooler hours of the day to conserve moisture.
- The study focused on diurnal plant movements, specifically how certain species of legumes respond to changes in light intensity by adjusting the orientation of their leaflets.

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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.