underlie
Americanverb (used with object)
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to lie under or beneath; be situated under.
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to be at the basis of; form the foundation of.
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Grammar. to function as the root morpheme or original or basic form of (a derived form).
The form “boy” underlies “boyish.”
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Finance. to be primary to another right or security.
verb
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to lie or be placed under or beneath
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to be the foundation, cause, or basis of
careful planning underlies all our decisions
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finance to take priority over (another claim, liability, mortgage, etc)
a first mortgage underlies a second
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to be the root or stem from which (a word) is derived
"happy" underlies "happiest"
Other Word Forms
Etymology
Origin of underlie
before 900; Middle English underlyen (v.), Old English underlicgan. See under-, lie 2
Explanation
While it’s true that when something underlies something else, it is beneath it, this does not necessarily mean subservience — it can also indicate a strong foundation or bedrock that underlies, or supports, an idea or decision. The Old English word underlicgan meant to serve or submit to another, and that meaning does carry through to the modern word underlie — to a point. Although still referring to something under something else, around 1850 the meaning of the verb shifted to include something that makes a foundation for something else. For example, one factor that underlies a patient's unusual symptoms might be his recent trip to a foreign country, where he could have picked up a local infection.
Vocabulary lists containing underlie
The Thing About Jellyfish
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"The Hand of Fatima" and "Old Ways, New World"
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Florida's B.E.S.T. Common Prefixes: under-
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
True open-source models allow full access to training data and code, while open-weight models share the numerical parameters, or “weights,” that underlie them.
From The Wall Street Journal • Mar. 18, 2026
Talk to some folks in your family whom you trust to make sure you’re not overstepping any unspoken boundaries that underlie family relationships.
From MarketWatch • Dec. 15, 2025
But the “frontier” language models that underlie ChatGPT and Gemini run in giant data centers, and are far too demanding for a phone.
From Barron's • Dec. 5, 2025
Morgan’s reply may be apocryphal, but it encompasses the truism that investors should divorce their emotional response to the markets from the cold analysis that should underlie investment decisions, if possible.
From Los Angeles Times • Mar. 18, 2025
For the first time, science could see the universal laws that underlie all of these little half laws.
From "Zero: The Biography of a Dangerous Idea" by Charles Seife
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
