Showing or characterized by persistent attention or untiring application: an assiduous worker who strove for perfection; did assiduous research before writing the book. See Synonyms at diligent.
[From Latin assiduus, from assidēre, to attend to : ad-, ad- + sedēre, to sit; see sed- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.