We drop the silent e from words when we add an ending beginning with a vowel. We keep it when we add an ending beginning with a consonant.
(excite-exciting and excitable but keep the e to become excitement)
There are some exceptions. Here are a few: words ending with -ee, –oe, –ye, –ge, –ce
see-seeing
agree-agreeing canoe-canoeist
dye-dyeing
manage-manageable
