Suffixes are added to the end of a word to change its function. They alter the tense of the verb from past to present, as in “call” and “called.” An adjective, "fortune," can become an adverb--"fortunately"--when it takes a suffix. Suffixes can also make a verb a noun as in “benefit” and “benefited,” or a noun an adjective, as in “pour” and “porous.” The rules for suffixes can be difficult to remember, especially when root words need to be changed before suffixes are added. There are exceptions, but here are a few rules you can use with most suffixes.
Learn to keep or drop a final silent e. Some words that end with a silent e change when suffixes are added, so look at the first letter of the suffix. If it starts with a vowel, drop the e. For example, drop the e from “inquire” when adding -ing so that it becomes “inquiring.” If the first letter begins with a consonant, retain the silent e. For instance, keep the e at the end of “manage” when adding –ment, so that it becomes “management.”
Practice suffixes with words that end in y. Make the “y” an “i” when the letter before the “y” is a consonant. For instance, change the “y” at the end of "beauty" to an “i” when you add the suffix -ful to spell “beautiful.”
Change adjectives that end in –ic to adverbs with the suffix –ally. For example, make “fantastic” an adverb with the suffix –ally, so that it reads “fantastically”.
Add the –ly suffix to adjectives that do not end in –ic. A word like hesitant takes the –ly ending to become “hesitantly.”
Look at the root word when using the suffixes –able and –ible. If the root can stand alone, it takes –able, as in “comfortable”. When the root cannot stand alone, use –ible as in “plausible”.
Write the final consonant twice in one-syllable words that end in a vowel-consonant sequence. The word “flat” is one syllable and ends in a vowel-consonant pattern, so add a “t” before the suffix –en to create “flatten.”
Do not double the final consonant if the suffix starts with a consonant. The suffix –ment begins with a consonant and, when it is added to “apart,” it does not take an extra "t" to spell the word “apartment.”