These resources cover how words change their form (typically by adding different endings) in different grammatical contexts. For example, the verb hop has the forms hop, hops, hopped and hopping.
If a root word ends in a consonant, adding a suffix will sometimes require that you double the base word’s final consonant.
How do you know when to double the consonant?
Consider the following examples, where doubled consonants are underlined.
shipment
shipped
muddy
fitful
fittest
waiting
greenest
Now take a look at some larger words, whose base forms have more than one syllable.
Suffixes cause many of our common spelling mistakes. One challenge is simply to know which is correct: for example, legible
or legable? In fact, −ible and −able serve the same function, and sound the same. As a matter of history, -ible entered English from Latin, while −able entered English from French, but there’s no easy rule for knowing when to use which suffix. Each word with each suffix just requires practice.