English is not a phonetic language but by and large there is a direct relationship between the spelling of a word and its sound. However, there are words which are not pronounced the same way they are written. For instance, PREY and PRAY are pronounced similarly but spelled differently and WIND is a word that conveys two totally different meanings and is also pronounced two totally different ways!.
The English language is peculiar as far as its grammar is concerned and there is a class of words which have some letters in their spellings which are not pronounced. These are the silent letter words. Here are some examples:
DOUBT is a word in which the sound of B is not made use of in the pronunciation.
KNEW is a word in which the sound of K is not pronounced.
SOLEMN is a word in which the sound of N is not pronounced.