1. The cardinal number equal to 3 + 1.
2. The fourth in a set or sequence.
3. Something having four parts, units, or members, such as a musical quartet or a four-cylinder engine.
All four limbs of an animal or person: a baby crawling on all fours.
[Middle English, from Old English fēower; see kwetwer- in the Appendix of Indo-European roots.]
four adj. & pron.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. 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.