It's important to note that the spelling of a word is not always an accurate guide to how it is pronounced. Similarly the pronunciation of a word is not always helpful when working out how that word should be spelt.
There are 26 letters in the English alphabet but there are many more sounds in the English language. This means that the number of sounds in a word is not always the same as the number of letters.
For example, the word 'CAT' has three letters and three sounds but the word 'CATCH' has five letters but still only three sounds.
If we write these words using sound symbols, we can see exactly how many sounds they have.
CAT is written - / kæt /
CATCH is written - / kæʧ /
In 'CATCH' the three letters TCH are one sound represented by one symbol / ʧ /