There are five distinct ways of pronouncing OO in English words. Usually OO occurs in the middle of words but is sometimes found at the end of words.

Pronunciation

1.   OO = /u:/ (long “oo”)

This is the most common and is pronounced as a long OO sound. This is the same as pronouncing the exclamation, “ooh.”

  • Cool
  • Soon
  • Zoom
  • Balloon
a. All words that end with OO are pronounced this way.
  • Yahoo
  • Kangaroo
  • Shampoo
2.   OO = /ʊ/ (short “oo”)

This is also pretty common. Think of this as a shorter version of “ooh.”

  • Foot
  • Wool
a. Letter groups that end with “k” or “d” are mostly pronounced this way.
Ending with “k”:
  • Book
  • Cookie
  • Mistook

Exceptions are spook (/spuːk/) and snooker (/ˈsnuː.kər/) 

Ending with “d”:
  • Good
  • Childhood
  • Understood

Exceptions are brood (/bruːd/), food (/fuːd/) and mood (/muːd/)

3.   OO = /ɔː/ (“open-o”)

There are several words where it is pronounced this way. This is the first part of “or” or “oar,” without the /r/.

  • Door
  • Floor
  • Poor
4.   OO = /ʌ/ (“a”)

There are only two words where it is pronounced this way. This is pronounced as an A instead of an O.

  • Blood
  • Flood
5.   Separated (2 o’s)

This usually occurs when 2 words (or a prefix to a word) are joined together. Here, the 2 O’s are split into separate syllables.

  • Cooperate
  • Zoology
  • Microorganism

Original posts: 2 October 2018