v. knew(n, ny), known(nōn), know·ing, knows
1. To perceive directly; grasp in the mind with clarity or certainty.
2. To regard as true beyond doubt: I know she won't fail.
3. To have a practical understanding of, as through experience; be skilled in: knows how to cook.
4. To have fixed in the mind: knows her Latin verbs.
5. To have experience of: “a black stubble that had known no razor” (William Faulkner).
a. To perceive as familiar; recognize: I know that face.
b. To be acquainted with: He doesn't know his neighbors.
7. To be able to distinguish; recognize as distinct: knows right from wrong.
8. To discern the character or nature of: knew him for a liar.
9. Archaic To have sexual intercourse with.
1. To possess knowledge, understanding, or information.
2. To be cognizant or aware.
in the know Informal
Possessing special or secret information.
know full well
To have complete knowledge of; understand completely: You know full well you're supposed to take off your shoes when you come inside.
know (someone) in the biblical sense
To have sexual relations with (someone).
you know Informal
Used parenthetically in conversation, as to fill pauses or educe the listener's agreement or sympathy: Please try to be, you know, a little quieter. How were we supposed to make camp in a storm like that, you know?
[Middle English knouen, from Old English cnāwan; see gnō- in the Appendix of Indo-European roots.]
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.