1. Relating to or occurring in a 24-hour period; daily.
2. Occurring or active during the daytime rather than at night: diurnal animals.
3. Botany Opening during daylight hours and closing at night.
1. A book containing all the offices for the daily canonical hours of prayer except matins.
a. A diary or journal.
b. A daily newspaper.
[Middle English, from Late Latin diurnālis, from Latin diurnus, from diēs, day; see dyeu- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.