A. Definitions

Alphabet - an ordered set of sound signs - named after first two letters in the Greek: alpha-beta [alef-bet]. A set of graphem-phoneme correspondences which allow a graphic shape to serve as a sound sign or phonogram.  In an ideal alphabet there is one and only one letter or symbol for each important sound in the language.

ALPHABET: A type of writing system in which a set of symbols [letters] represents the important sounds [phonemes] of a language.           DICTIONARY OF LANGUAGE & LANGUAGES BY DAVID CRYSTAL 

Unifon means one sound and indicates one sound per symbol.  In many writing systems there is only one sound per symbol.  In English there are over 14 sounds per symbol.  The English writing system has 106 symbols for 40 or so sounds.  The problem is that the same symbol can refer to more than one sound. 
 

Polyvalence in the traditional English writing system

Letter	Sound	Sample	Sound	Letter	Sample
A	ae	cat	/i:/	ea	tea
	a:	bath		ee	see
	ei	able		ey	key
	o	quality		e	me
	o:	all		ie	siege
	e@	care		ei	seize

Polyvalence means multiple values: Letters are associated with multiple sounds, sounds are associated with multiple letters.  For more inconsistencies see uu18ways
 
Languages are 100% phonemic.  Visualized speech is phonemic or alphabetic to the extent to which it mimics the phonological structure of a language. The writing systems for most languages are over 85% phonemic.  According to Laubach, an international literacy teacher, English has the world's worst alphabet.  English is only about 40% phonemic. [Dewey]

A writing system is phonemic to the extent to which it is consistent with its pronunciation guide.  No phonemic pronunciation guide for English matches traditional written English more than 40% of the time.  Truespel matches English only 7% of the time.  Phonemic Spanglish matches about 30% of the time.

Stability of Grapheme Phoneme Correspondences - Word pronunciation changes over time. To retain a consistent alphabetic correspondences, some words must be respelled. The time interval often depends on contact with other speech communities. Spelling adjustments (reform) usually needed every 50 to 100 years. Changes simplify spelling and learning but habits are difficult to change

No alphabet is stable. Any alphabet used by peoples with different language heritages undergoes modification. If left unchecked, these word pronunciation changes will lead to a degeneration of the alphabetic principle. Most languages need to be adjusted every 50 years or so to maintain the alphabetic principle. It has been 400 years since English was standardized at the word level.  It has not been standardized below the word level for 1000 years.

This begins to account for the high number of inconsistencies and irregularities found in the orthography.

Sounds and symbols - There are only 26 letters in the English alphabet and of these c, x, and q are duplications. There are 38–50 sounds to be represented.  With digraphs, 23 letters would be sufficient if the letters were used rationally. 

Some of the inconsistencies are shown in the table above.  The inconsistency in found primarily with vowels. For instance, the vowel sound in 'set' is represented by e in 'set'; by a in 'many'; by ea. in 'feather'; by ai in 'said'; by ei in 'heifer'; by eo in 'leopard'; and by ay in 'says'. In the 20th century there have been protests for spelling reform, but there has been little progress.

a: [ei] in hating, [a:] in father, [o:] in water, [e] in many, [æ] in hat, [o] in want, ['] in brilliant, [e] in various, [i] in village.     
heiting, faather, woter, menny, hatt, wont, brillyant, verrias, villi
hEtiN   fxDcr   wxtcr   menE   hat   wont   brilicnt   verEus   vilij

ae: [i:] in minutiae, [e] in aerial, [ei] in Israeli   minUSc   izrAlE

ai: [ei] in sail, [e] in said, [æ] in plait, [ei] in dais, [ai] in aisle, [a:ii:] in naive

ao: [ei] in gaol /jeil/, [eio] in chaos [kaos], [u/ou] in pharaoh /ferrow/   ferO

au: [ei] in gauging /geijiq/, [a:] in aunt, [o:] in haul, [u/ou] in chauffeur /showfr/, [o] in laurel   [gAjiN xnt, hxl, shOfcr, lxrcl]

aw: [o:] in awful  /olfwl/   paw, crawl [see all]  aa+u  close to [oh]  sao=sau

ay: [ei] in pray, [e] in says  [prey, sez]      hi sez hi preiz - hE sez hE prAz

e: [i:] in be, [i] in pretty, [e] in let, ['] in open   [bi, pritty, lett, oup'n/'up'n]

ea: [i:] in heal, [ei] in great, [i] in guineas, [e] in head, [i:æ] in react, [i] in area, [i:ei] creator

eau: [u/ou] in beau, [ju:] in beautiful /byutifwl/  [ref: eh+ah+u  @u]

ee: [i:] in feet, [i] breeches