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oc·clu·sion (ə-klzhən)
Share:
n.
1.
a. The process of occluding.
b. Something that occludes.
2. Medicine An obstruction of an anatomical passage, as of an artery by plaque.
3. Dentistry The alignment of the teeth of the upper and lower jaws when brought together.
4. Meteorology
a. The process of occluding air masses.
b. An occluded front.
5. Linguistics Closure at some point in the vocal tract that blocks the flow of air in the production of an oral or nasal stop.

[From Latin occlūsus, past participle of occlūdere, to occlude; see OCCLUDE.]
(click for a larger image)
occlusion
top: in a cold-front occlusion cold air moves under a mass of warm air and under the cool air in front
bottom: in a warm-front occlusion cool air moves under a mass of warm air while riding over the cold air in front

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:

    Indo-European Roots

    Semitic Roots

    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.