What’s the rule of converting a verb into noun o adjective? Especially, when do we add double consonant in front of ‘ing’, for example, we use the word ‘stopping’ but not ‘jumpping’, but both words original forms are stop and jump. So what’s the difference?

Question

Answer

English vowels have two pronunciations - their sound and their name.
Fir example, the sound of 'u' is as in 'jump' while the name of 'u' is as in 'university'.
The vowel in 'jump' is followed by a double consonant. This means that it is pronounced like the sound of the vowel, not the name of the vowel, when 'ing' is added.
The vowel in 'stop' is only followed by one consonant so, if you add 'ing' without doubling the 'p', the 'o' will be pronounced like its name (like in 'hope').