1. The letters _f_, _l_, or _s_ at the end of words of one syllable
and after a single vowel are usually double; as, muff, ball, grass.
2. Words ending in _e_ usually drop it on adding _ing_ or any other
suffix beginning with a vowel; as, come, coming; bride, bridal;
love, lovable.
3. Words of one syllable, and words accented on the last syllable,
if they end in a single consonant with a single vowel before it,
usually double the final consonant on adding _ing_, _ed_, or any
other suffix beginning with a vowel; as, rob, robbed; mad, madden;
admit, admitting; begin, beginner.
4. Words in _y_ with a consonant before it usually change the _y_
into _i_ when a suffix not beginning with _i_ is added; as, cry,
cries, crying.
5. The apostrophe (') is used to indicate the omission of one or
more letters; as, didn't for did not; can't for cannot; let's, let
us; I'm, I am; you're, you are; isn't, is not.