1. A word formed by combining the initial letters of a multipart name, such as NATO from North Atlantic Treaty Organization or by combining the initial letters or parts of a series of words, such as radar from radio detecting and ranging.
2. Usage Problem An initialism.
ac′ro·nymic, a·crony·mous (ə-krŏnə-məs) adj.
Usage Note: In strict usage, the term acronym refers to a word made from the initial letters or parts of other words, such as sonar from so(und) na(vigation and) r(anging). The distinguishing feature of an acronym is that it is pronounced as if it were a single word, in the manner of NATO and NASA. Acronyms are often distinguished from initialisms like FBI and NIH, whose individual letters are pronounced as separate syllables. While observing this distinction has some virtue in precision, it may be lost on many people, for whom the term acronym refers to both kinds of abbreviations.
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.