a. In certain languages, the inflection of nouns, pronouns, and adjectives with respect to categories such as case, number, and gender.
b. A class of words of one language with the same or a similar system of inflections, such as the first declension in Latin.
2. A descending slope; a descent.
3. A decline or decrease; deterioration: "States and empires have their periods of declension" (Laurence Sterne).
4. A deviation, as from a standard or practice.
[Middle English declenson, from Old French declinaison, from Latin dēclīnātiō, dēclīnātiōn-, grammatical declension, declination; see DECLINATION.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.