The letter Y is the 25th letter in the English alphabet. It is a vowel, but can also be used as a consonant. In English, Y is an interesting letter because it is not pronounced as /y/ any longer, but rather as /wi:/. This change in pronunciation came with the 'Great Vowel Shift' in England between 1350-1500 AD.
The letter Y can be traced back to the Semitic alphabet and was the letter Waw. This is something that many other letters are based on, including F, V and U. The Phoenician letter is the basis for the Greek and the Latin alphabets.
The shape of the letter has never really changed, since the Semitic sign is what we know as a capital Y. There are now a few looks to the letter – the main one being a vertical stick with two diagonal lines at the top for the capital letter. The lower case version has a couple of forms – a single story and double story version. It is basically a small Q but with a curl to the left, like the letter G. This can then be turned into the double story by adding a loop and is commonly used with joined up hand writing.
The Y is sometimes considered to be a vowel and is used in some smaller words like fly and sky, without any other vowels – every word needs to have a vowel in it. This is where the idea of six vowels in the English alphabet comes from.
Y is also commonly used in mathematics, especially in algebra. It is commonly used in formulas when there are two unknowns. It is also used in graph work as the vertical scale and in geometry.
Despite its peculiarity, the Y is rather common in english words, although there are only two Y in the standard Scrabble letter pouch. The Y yields 4 points, which is fair. Together with an L, the Y can be used to create many adverbs from adjectives, like "slow" becomes "slowly", and "stubborn" becomes "stubbornly".