The Complete Guide to English Spelling Rules

(^) In the ieu group, we have a very small group of words that are mostly of French origin:
(^) An unusual but very ancient pair of words use the om spelling to achieve the oo sound—tomb and
womb.
There is a very large group of words that use the eu spelling. Most of these are scientific words, but
there are quite a number of words in general use:
(^) A very small group of words uses ui to achieve the oo sound:.
(^) The ua group of words can be eliminated because ua is not a true diphthong; i.e., it is pronounced not
as one syllable, but two. There are many words that contain this vowel combination, but in most cases the
al is a suffix and when pronounced correctly, does not produce the oo sound.
(^) A note on pronunciation. There will always be differences of opinion regarding the correct
pronunciation of the oo sound. With some words, it is clearly an oo sound, whereas with others the sound
is closer to uh. Compare wound and would. This is a matter of personal preference and does not affect the
spelling.
In review, we can see that the eighteen possible combinations can be reduced to a mere half dozen
important spellings that group themselves into logical patterns.