There are several rules concerning words ending in y, knowledge of which will aid us greatly in spelling.

1. Words ending in ie change the ie to y before ing to prevent a confusing number of vowels. For example, die, dying; lie, lying; tie, tying.

2. Words of more than one syllable ending in y preceded by a consonant, change y into i before all suffixes except those beginning with i. For example:

happy,happily,happiness;
witty,wittier,wittiest;
satisfy,satisfied,satisfying;
envy,enviable,envying;

This exception is made for suffixes beginning with i, the most common of which is ing, to avoid having a confusing number of i's.

3. Most words ending in y preceded by a vowel retain the y before a suffix. For example:

destroy,destroyer,destroying,
buy,buyer,buying,
essay,essayed,essayist.

The following words are exception to this rule: