si·mul·ta·ne·ous (sī′məl-tānē-əs, sĭm′əl-)
1. Happening, existing, or done at the same time. See Synonyms at contemporary.
2. Mathematics Containing variables for which there are values that can satisfy all the equations: simultaneous equations.
[Latin simul, at the same time; see sem-1 in the Appendix of Indo-European roots + English -taneous (as in INSTANTANEOUS).]
si′mul·tane·ous·ness, si′mul·ta·nei·ty (-tə-nēĭ-tē, -nā-) n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.