The I before E rule in English Spelling by Vivian Cook

The I before E Rule	WSTopics Home Vivian Cook
The only spelling rule that most English-speaking people consciously know is the familiar 'i' before 'e' except after 'c'. Try it out on this sample to see if it works

recieve receive

niece    neice

grief    greif

caffiene    caffeine

deciet    deceit

field    feild

believe    beleive

wiegh    weigh

cieling    ceiling

sieze    seize

biege    beige

percieve    perceive

Answers: <ie> niece, grief, believe, species, field; the rest <ei>

To explain these, the rule needs to be modified

1. It only works when 'ei' goes with the long 'ee' sound of eel. So it does not apply to weigh, beige, or indeed to many words with vowel plus silent 'g': sleigh, eight, reign, neigh. So the rule needs to be:
           'i' before 'e' except after 'c' when 'ei' is said with a long 'ee' sound
2. A few words have 'ei' rather than 'ie' despite having the long 'ee' sound: seize, caffeine

3. It doesn't apply to plural 'es' currencies, policies; to diphthongs society, science; or when 'c' is said as 'sh' as in sufficient ancient, proficient

Percentage of mistakes on web pages for some test words

receive 1.8%

deceive 2.5%

niece 8.7%

seize 1.7%

conceive 2.3%

perceive 1.9%

receipt 0.6%

ceiling 0.3%

caffeine 2.9%

Compared with other difficult words such as supersede, these percentages seem quite low. Either people have learnt the rule very well, including its exceptions, or it does not really give much difficulty. In any case at best it is a very minor rule that affects a small proportion of words. Only 11 of the top 10,000 words in the British National Corpus for example have 'cei' spelling.

recieve receive	niece neice	grief greif
caffiene caffeine	deciet deceit	field feild
believe beleive	wiegh weigh	cieling ceiling
sieze seize	biege beige	percieve perceive
Answers: <ie> niece, grief, believe, species, field; the rest <ei>
To explain these, the rule needs to be modified	1. It only works when 'ei' goes with the long 'ee' sound of eel. So it does not apply to weigh, beige, or indeed to many words with vowel plus silent 'g': sleigh, eight, reign, neigh. So the rule needs to be: 'i' before 'e' except after 'c' when 'ei' is said with a long 'ee' sound 2. A few words have 'ei' rather than 'ie' despite having the long 'ee' sound: seize, caffeine 3. It doesn't apply to plural 'es' currencies, policies; to diphthongs society, science; or when 'c' is said as 'sh' as in sufficient ancient, proficient
Percentage of mistakes on web pages for some test words	receive 1.8%	deceive 2.5%
	niece 8.7%	seize 1.7%
	conceive 2.3%	perceive 1.9%
	receipt 0.6%	ceiling 0.3%
	caffeine 2.9%
Compared with other difficult words such as supersede, these percentages seem quite low. Either people have learnt the rule very well, including its exceptions, or it does not really give much difficulty. In any case at best it is a very minor rule that affects a small proportion of words. Only 11 of the top 10,000 words in the British National Corpus for example have 'cei' spelling.