a·dult (ə-dŭlt, ădŭlt)
1. One who has attained maturity or legal age.
2. Biology A fully grown, mature organism.
1. Fully developed and mature.
2. Relating to, intended for, or befitting adults: adult education.
3. Containing or dealing in explicitly sexual material; pornographic: adult movies.
[From Latin adultus, past participle of adolēscere, to grow up; see ADOLESCENT.]
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.