Mark Scheerer writes in response to my column on the 20th anniversary of the World Wide Web: "Tim Berners-Lee says his friends gave him a hard time because his term, World Wide Web, 'yielded an acronym that was nine syllables long when spoken.' I believe it actually yielded an abbreviation or a set of initials -- not an acronym, or letters which form a word."

Acronym is one of those words that has remained maddeningly ill-defined for its entire existence. Like my predecessor William Safire, I prefer defining acronym as “a pronounceable word created out of the initials or major parts of a compound term, like NATO, radar or TriBeCa.” When the abbreviation is pronounced by the names of initial letters, like C.I.A. (“see eye ay”), U.C.L.A. (“you see ell ay”) or the unwieldy WWW (“double-u double-u double-u”), then it’s best to call it an initialism. This is the nomenclature preferred by many abbreviation-watchers, including the creators of the “Acronyms, Initialisms and Abbreviations Dictionary,” first published in 1960.

Not everyone is on board with the acronym vs. initialism distinction, however. Another definition of acronym is more expansive, encompassing any abbreviation formed from initial letters regardless of pronunciation. Even language specialists occasionally prefer this watered-down version of acronym. For instance, Grover Hudson’s “Essential Introductory Linguistics” divides the broader category of “acronyms” into “word acronyms” (the kind pronounced as words, like radar), and “spelling acronyms” (another name for “initialisms” like WWW).

Though initialism is the older term, it has never caught on in wider usage, which is part of the problem in getting people to see eye to eye on the distinction between acronyms and initialisms. The earliest known use of initialism is from 1844, in an article in “The Christian’s Monthly Magazine and Universal Review” discussing SPQR, an abbreviation of the Latin phrase Senatus Populusque Romanus ("The Senate and People of Rome").