Many words in English were spoken before they were written. And also many words deviated from their intended pronunciation after the "great vowel shift" English has also taken words from other languages. These words adopt a English pronunciation but the spellings stay true to their original form.

Do you guy see the thread here? Not to be offensive but you are all misinformed or did not understand the question. Don't you realize how frustrating this is to italki students??? This is why many of my students come to me discouraged and let down. If you don't fully know the answer and if you know you are just saying something to sound right please stop! If the student studies English long enough, they will hear the facts eventually and remember how right you tried to sound but how misleading you really were. wishing to "hear" yourself be right is not the same as being right. Please fellow educators hear me out, "humility is a good thing to practice." Sometimes the best thing you can do for your students is tell them, "I don't think I have an answer." The main reason for homographs (words with the same spellings, but different pronunciations) is as follows: All these words were spoken before they were written, so I do not think that the spelling affects the pronunciation. It probably has more to do with the pronunciation of the words from which they evolved. For example, "earth" is derived from words which did not contain the letter "a" when written down. In German, the word is "Erde". "Hearth" is etymologically related to "carbon" (burning etc), which might explain why the "ea" is pronounced differently in that word.

The pronunciation really depends on the context in which a word is used and the letters (if any) preceding and following 'ea' - for example, in the words 'head and 'lead' (the metal) the 'ea' sound differs again from the pronunciation of the examples quoted - 'great' and 'meat'. In another context 'lead' (to lead someone) will be pronounced differently 'lead' the metal.

/ei/ However, while 'gray' and 'grate' are the same pronunciation, depending upon emphasis, I may say 'great' either is /ei/ or I will make it more sounding like two-syllables with an elongated diphthong /ei & i:/.

"ea" is not only pronounced /ei/ in " Great" but also in many other words. For examples: Steak, Break, Breaker =) in my opinion, there's no emphasis here. It's simply like the letter "a" . In " Cat " it's pronounced /æ/ , in " May" it's pronounced /ei/ and in " Car" it's pronounced /a:/.