In this chart attention is drawn to the fact that most speakers of English slur the a in words such as medical and manage. This can lead to difficulties in their correct spelling.
As it is the spelling of the language which keeps it secure, it is important to draw attention to the fact that many words are pronounced differently in different parts of the English-speaking world.
Grass and banana, for example, are pronounced phonetically in the USA and Canada but as gras and barnarna in most parts of England and Australia.
The chart above is particularly useful for people who can read fairly well but whose spelling skills are poor.
See The Manual for full details of its proper use.