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val·id (vălĭd)
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adj.
1. Well grounded; just: a valid objection.
2. Producing the desired results; efficacious: valid methods.
3. Having legal force; effective or binding: a valid title.
4. Logic
a. Containing premises from which the conclusion may logically be derived: a valid argument.
b. Correctly inferred or deduced from a premise: a valid conclusion.
5. Archaic Of sound health; robust.

[French valide, from Old French, from Latin validus, strong, from valēre, to be strong; see wal- in the Appendix of Indo-European roots.]

va·lidi·ty, valid·ness n.
valid·ly adv.

Synonyms: valid, sound2, cogent, convincing
These adjectives describe assertions, arguments, conclusions, reasons, or intellectual processes that are persuasive because they are well founded. What is valid is based on or borne out by truth or fact or has legal force: a valid excuse; a valid claim.
What is sound is free from logical flaws or is based on valid reasoning: a sound theory; sound principles.
Something cogent is both sound and compelling: cogent testimony; a cogent explanation.
Convincing implies the power to dispel doubt or overcome resistance or opposition: convincing proof.

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:

    Indo-European Roots

    Semitic Roots

    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.

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