Apostrophes

Periods are most commonly found at the end of sentences.
However, they have other uses.  Periods can be used in the
following ways:

Signal the End of a Complete Sentence

• The dog runs fast.
  
• The boys studied mathematics.
  

Initials

• J.P. Franklin
  
• I.M. Pei
  

Abbreviations and Acronyms

• Y.M.C.A.
  
• U.S.A.
  
• P.E.T.A.
  
• Dr.
  
• Mr.
  
• Mrs.