English has 44 sounds and only 26 letters to represent them. That means that there is no one-to-one matching of sounds and letters and some letters are used for more than one sound.
For instance, the letter G can be used for the hard ‘g’ in rug and the soft ‘j’ in germ.
The letter S can be used for the hissing sound in sit and the buzzing sound in pheasant.
Some sounds can be shown by more than one letter, or letter combination:
The sound ‘ai’ can be shown as eye, aisle, I, guy and might, while the sound ‘f’ can be shown as in feel and photograph.
However, some words that sound the same can be written differently:
their/there/they’re tide/tied hare/hairair/heir
Some letters have become silent over the centuries as the pronunciation of words has become simplified, but the spelling of these words has remained the same:
G is silent in gnome
K is silent in knight
H is silent at the beginning of most words, as in honest
Some letters can be doubled, but there may be no difference in pronunciation: robin rabbit
These oddities in English spelling were demonstrated in the nineteenth century when someone realized that the word ghoti could be pronounced as fish. This made-up word, although it looks nothing like fish, can be given that pronunciation when you break it down into three parts:
gh as in rough
o as in women
ti as in condition
…so ghoti = fish!
Although there is something rather fishy about this spelling it shows rather well some of the strange spelling rules in English that come from using just 26 letters to show 44 sounds.