thereof
Americanadverb
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of that or it.
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from or out of that origin or cause.
adverb
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of or concerning that or it
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from or because of that
Usage
What does thereof mean? Thereof means of, from, because of, or concerning the thing that was just mentioned, as in The warranty covers the device and the parts thereof (translation: The warranty covers the device and the parts of the device). Thereof is fairly formal. It’s often used in legal language, but it can also be used in everyday speech and writing. Thereof is perhaps most commonly used in the phrase lack thereof, meaning the lack of the thing just mentioned. This is used in cases in which something is mentioned in a general way but the situation being discussed involves the lack of that thing, as in Most relationship problems are due to communication, or a lack thereof (translation: Most relationship problems are due to communication issues, specifically a lack of communication). Other common phrases that use the word are combination thereof (meaning a combination of the things just mentioned) and portion thereof (meaning a portion of the things just mentioned). Example: My research is focused on investigating the cause of the disease and the effects thereof.
Etymology
Origin of thereof
before 1000; Middle English therof, Old English thǣrof. See there, of 1
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.
According to this school of thought, his main qualification was a lack thereof.
From Slate ● Jul. 8, 2026
There have been niceties and brownnosing, but no sanctions or threats thereof.
From Los Angeles Times ● Jun. 22, 2026
One answer, new research suggests, is affordability—namely, the lack thereof.
From Barron's ● May 27, 2026
“This highlights that chimpanzees have a sense of group identity that goes beyond familiarity or lack thereof, which, as in humans, can reorganize in the face of changing relationships and social contexts.”
From Salon ● Apr. 23, 2026
The next problem was heat, or the lack thereof.
From "The Martian" by Andy Weir
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.
