triphthong

• Ou, as ought, not, out Au is put for ao, ou for au, as sauce, souce Eu or ew, ewe, neuter, is right Iu, as view, might be mended thus, viu Ou is common, as could, cow, but there is difference between o long and short O is often us’d for a triphthong (y in British). —  Magazine, or Animadversions on the English Spelling (1703)
• The triphthong is properly a union of letters, not sounds OF THE VARIOUS SOUNDS All the vowels, and some of the consonants, have several sounds; in this book these sounds are indicated by diacritical marks, as in the following tables TABLE OF VOCALS. —  McGuffey's Eclectic Spelling Book
• A triphthong is PROPER if all three of the vowels are sounded. —  Orthography As Outlined in the State Course of Study for Illinois
• A triphthong is IMPROPER or is called a TRIGRAPH if one or two of the three vowels is silent; as in ad_ieu_, b_eau_ty. —  Orthography As Outlined in the State Course of Study for Illinois
• O is often us’d for a triphthong (y in British). —  Magazine, or Animadversions on the English Spelling (1703)

Used in the Same Context