SATURDAY, AUGUST 08, 2020 - https://www.dictionary.com/e/word-of-the-day/
[ dif-thawng, -thong, dip- ]
an unsegmentable, gliding speech sound varying continuously in phonetic quality but held to be a single sound or phoneme, as the oi-sound of toy or boil.
WHAT IS THE ORIGIN OF DIPHTHONG?
Diphthong is hard enough to spell and pronounce, let alone define. Diphthong ultimately comes from Greek díphthongos, literally “with or having two sounds,” a compound of the Greek prefix di- “two, twice, double” and the noun phthóngos “voice, sound,” a derivative of the euphonious verb phthéngesthai “to utter a sound, raise one’s voice, call, talk.” Phthéngesthai is also the root of the Greek verb apophthéngesthai “to speak one’s opinion plainly,” whose derivative noun apóphthegma “a brief, pointed saying” comes into English as apothegm or apophthegm, even harder to spell and pronounce than diphthong. Phthéngesthai has no convincing etymology, but some scholars point to “phonetically convincing” Lithuanian žvéngti “to neigh” and speñgti “(in the ears) to resound, hum, drone.” (The Lithuanian and Greek words derive from the Proto-Indo-European root ghwen-, ghwon- “to sound.”) Diphthong entered English in the second half of the 15th century.
HOW IS DIPHTHONG USED?
The best word ever—according to deep lexicographical research, science, taste, and common sense—is this: diphthong. - MEGAN GARBER, "HERE IT IS: THE BEST WORD EVER," THE ATLANTIC, SEPTEMBER 13, 2012
It [Atlas of North American English] is vast enough to include 139 color-coded maps and software that lets users click around the country to hear native speakers drop their r’s and overextend their diphthongs with abandon. - TAMMY LA GORCE, "YA GOTTA BLAME NEW YORK FOR DAT," NEW YORK TIMES, FEBRUARY 12, 2006