There is no letter “OO” in the English alphabet, but Long-OO and Short-oo are part of the vowel system.

Short-oo

Short-oo is a unique vowel sound that is not represented by any other vowel letter. This vowel is explained in “Short-oo? What’s that?”

Long-OO

Long-OO does not have its own sound. It uses the Long-U-2 sound. Long-OO is really more of a “helper” to Long-U — it’s an alternate way to spell the Long-U-2 sound. Long-OO takes the place of the letter “U” in words that need a Long-U-2 instead of Long-U-1. (see Long-U: 1 or 2?). Here are some examples,

fool  — If we spelled this word with a “U”, the “F” would trigger a Long-U-1, and the word would end up sounding like the word “fuel”. So, in order to have a Long-U-2 sound in “fool”, the “OO” is used instead of a “U”.

boot — If this word had a “U” it would be “bute” — because a “B” also requires Long-U-1. So again, the “OO” helps out to keep a Long-U-2 sound.

coo — This word would sound like “cue”, if it had a “U” instead of “OO”.

Spelling Patterns

Long-OO and Short-oo also sometimes follow spelling patterns used by the other vowels. For example, the spelling rule in which an [-e] at the end of a word indicates a long vowel, can also be seen in some words with “OO”:

• If you see an [-e] at the end of a word with “OO” you know for sure that it is Long-OO, as in the words “soothe”,  “goose” and “snooze”.
• However, if you see a word that does not have an [-e] at the end, it could have either sound. Some have Long-OO, such as “food”, “school” and  “moon”. Some have Short-oo, such as “hook”, “wool” and “good”.

So that’s the scoop on Long-OO.