pro·long (prə-lông, -lŏng)
tr.v. pro·longed, pro·long·ing, pro·longs
To lengthen in duration; protract: factors that prolong the drug's effect.
[Middle English prolongen, from Old French prolonguer, from Late Latin prōlongāre : Latin prō-, forth; see PRO-1 + Latin longus, long; see del-1 in the Appendix of Indo-European roots.]
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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.