thresh·old (thrĕshōld′, -hōld′)
1. A piece of wood or stone placed beneath a door; a doorsill.
2. Either end of an airport runway.
3. The place or point of beginning; the outset: on the threshold of a new era.
4. The point that must be exceeded to begin producing a given effect or result or to elicit a response: a low threshold of pain.
[Middle English thresshold, from Old English therscold, threscold; see terə-1 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.