1. Occurring, encountered, done, or taken from time to time; irregular or infrequent. See Synonyms at periodic.
2. Created for a special occasion: occasional verse.
3. Intended for use as the occasion requires: an occasional chair.
4. Being a factor that makes something possible; being a cause of something.
5. Acting in a specified capacity from time to time: an occasional hunter.
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.