What is a long vowel? This is a deceptively easy question: a long vowel is a vowel that is pronounced for a long period of time, about twice as long as a short vowel. Length is a question of duration. The problem, for English at least, is that reading teachers (and others) use the term "long vowels" to mean something else, what linguists call "tense vowels." Why? Blame the Great Vowel Shift. As result of the changes we have been describing, two important things happen: 

1. Vowel length ceases to be meaningful (that is, phonemic) in English

 
2. Our spelling system, which became standarized while the Shift was taking place, doesn't match the vowel system that exists now.

So, when you're thinking about vowel length from a linguistic perspective, you need to forget everything you may have learned about so-called "long" and "short" in phonics. When we talk about long vowels in this web site, we mean looooooong vowels, vowels are pronounced for a long period of time.

By the way, we really like reading teachers. It's not their fault that the Great Vowel Shift makes teaching reading so difficult.

What is this trapezoid? The vowel trapezoid is a stylized representation of the mouth. The left edge is the front of the mouth (imagine teeth); the right edge is the back. The top is the top of the mouth, etc. The placement of a character within the trapezoid reflects the position of a person's tongue in the mouth when that vowel is being pronounced. For example, the high front vowel /i/ is placed up in the top left corner of the diagram.

We didn't make up the vowel trapezoid; it is a standard diagram and will appear in any linguistic text that discusses phonetics or phonology. Different scholars use different dimensions for the boundaries of the trapezoid; we are using a very simple shape.

What do these "letters" represent? First things first--those are characters, not letters. They are characters in the IPA, the International Phonetic Alphabet. The characters represent sounds; they are NOT equivalent to the letters of the English alphabet. The joy of the IPA is that each character represents one and only one sound: /i/ is the sound in "beet" or "machine," not the sound in "bit" or "motion" or "I." Any linguistics or history of the English language text will introduce you to the IPA. Of course, you can click on any of the buttons on the See and Hear page to hear the sound a character represents. 

For a useful introduction to modern American English vowels, see Symbols for American English Vowels, part of Studying Phonetics on the Net.

What is PDE? Present-Day English. Just for the record, when we say Present-Day English, we mean General American English, because that's what we happen to speak.  For the purposes of this web site, dialect differences shouldn't be a problem, but if you are unfamiliar with American English vowels, you should check out the useful Symbols for American English Vowels, which allows you to hear the vowels.  By the way, ME is Middle English, MnE is Modern English, and EMnE is Early Modern English.