METRO Spelling and Pronunciation

Note: when identifying letter forms, the convention is to enclose them in acute-angled brackets < >.

i/j (consonant)

<i> could be not only the vowel but also the consonant: ioy, iangling. There was not yet a separate letter <j> for the consonant.

i/y (vowel)

<y> and <i> are interchangeable as vowels: hym = him 
But <y> can also be the consonant as in ye, yere, yong

u/v

<u> and <v> were not yet distinguished as two separate letter forms but as alternate ways of writing one letter. (This is why today we still call the letter <w> double-u!) So each could signify the consonant or a vowel. Their distribution depended on where they appeared in a word. The form <v> was preferred as an initial letter: vs, vnkind, vnder; <u> was used anywhere else: haue, euil, euer, heauen.

th, ch, sh

Digraphs <th, ch, sh> have their familiar MnE values; sometimes <sch> = <sh>.
<gh> is most often a fricative as in Scots loch or German ich.

wh

<wh> is the post-Conquest substitute for the Old English <hw> but the pronunciation [hw] is usually maintained in ME.

dg/gg

<dg> in words like edge may be spelled <gg>

initial g, k

initial <k> in words like know, knee and <g> in gnash were pronounced

ou/ow

<ou> and <ow> could each signify a long [u] in ME: you, yow, about, abowt. 
There are some exceptions, particularly words that today are pronounced as [o] and spelled <ow>, such as snow, know.

double vowels

Doubling a vowel is one way to indicate length, but not always found: 
gode/good, dore/door, one/oone, slepe/sleep, grene/green, life/liif, made/maad.

final -e

A fourteenth-century love lyric called "Alysoun" contains a line in which every word ends with -e:

On heu hire her is fayr ynoh,
hire browe broune, hire eye blake;

(In color her hair is fair enough,
her brow brown, her eye black.)

If the reader pronounces every -e as a separate syllable, the second line would have twelve syllables, instead of the eight syllables the verse line calls for. How do we decide which -e to pronounce? Meter can provide a good guide. The line below uses red to indicate a stressed syllable:

hire browbroune, hire eyblake;

Why does the scribe bother to write a final -e on words where is not pronounced? In some instances (like hire) the final -e is a remnant of an inflected ending, so it has some historical precedent. In other instances (like broune) the final -e is scribal—that is, it is added at the whim of the scribe, who may very well spell it without the final -e the next time it is written.

So the rule of thumb for the final -e is to pay attention to the meter of the line and pronounce it where needed. In prose there is no such guide, and even the experts are not always sure how to pronounce every final -e.

long e

The long <e>, as in flee, was pronounced like modern long <a>.