Pronunciation: [ˈʌpsɪlˌɔ͡ɪd] (IPA) 
The word "upsiloid" is spelled with the letter "u" in place of the usual "y" in the root word "upsilon." This change occurs because "upsiloid" is a derived word meaning "resembling upsilon," which is a Greek letter that looks like a "Y." When spelled using the International Phonetic Alphabet (IPA), "upsiloid" is written as /ʌpsɪlɔɪd/, with the "ʌ" representing the "u" sound and "ɔɪ" representing the "oy" sound.
Upsiloid is a term often employed in the field of linguistics and phonetics, referring to a speech sound that possesses characteristics similar to the vowel known as "upsilon" (/ʌ/ in IPA notation). The term "upsiloid" is derived from the Greek letter "upsilon" (υ), which represents the sound /ʌ/ in Greek.
In phonetics, "upsiloid" describes a vowel sound that shares certain acoustic qualities with the upsilon vowel. These shared characteristics could include a similar position of the tongue, lip rounding, or other articulatory features. However, an upsiloid sound is not necessarily the exact same as the upsilon vowel, as it may have slight differences in terms of duration, intensity, or frequency.
The term "upsiloid" also finds application in the study of languages where a vowel resembling upsilon exists, but the original phonemic distinction has been lost or altered. In these cases, the term may be used to categorize the sound as upsiloid to highlight its similarity to the upsilon vowel. Additionally, upsiloid can designate a sound produced in a specific dialect or idiolect, which is akin to, but not identical to the typical upsilon vowel.
Overall, "upsiloid" refers to a speech sound that exhibits phonetic resemblance or similarity to the vowel upsilon, either in terms of articulation, acoustic properties, or historical phonemic relationship.
Hypsiloid.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
