This field of study is called "orthographic depth". The orthographic depth of an alphabetic script is the degree to which a written language deviates from simple one-to-one letter–phoneme correspondence. It shows how easy it is to predict the pronunciation of a word from its spelling. Shallow orthographies are easy to pronounce based on the written word, and deep orthographies are difficult to pronounce based on how they are written. In shallow orthographies, the spelling-sound correspondence is direct: given the rules of pronunciation, one is able to "say" the word correctly.