1.  Upsīlon is the twentieth letter in the Greek alphabet.

2.  Upsīlon is a variable vowel and voiced as are all vowels. Thus, the vocal cords always vibrate when pronouncing the letter's phoneme. It may be pronounced either long or short. Further phonetic principles will be later explained in future lessons to help when it is pronounced long or short.

3.  Upsīlon's long phoneme is pronounced as the "u" in "lute." Its short phoneme is pronounced as the "u" in "put." Whether long or short, its phoneme is aspirated when it is the first letter in a word and is pronounced like the "u" in "hubris."

4.  Upsīlon's lower case letters may be easily confused when written. Special care needs to be exercised. Form upsīlon with a rounded bottom with the right upward stroke turned outward.

5.  Upsīlon's capital letter should not be confused with the English capital letter "Y." Greek does not have an alphabetical letter that corresponds to the English "Y."

6.  Upsīlon is transliterated as "Y" or "y" except in the diphthongs αυ, ευ, and ηυ where it is instead transliterated as "u." If upsīlon is the initial word's letter, then it is transliterated as "hu" to reflect its aspiration.