Full Stop or Period

1. Use a full stop at the end of a sentence:

• The man arrived. He sat down.

2. Use full stops with abbreviations (in an abbreviation the last letter of the word and of the abbreviation are not the same):

• Co. (Company)
• etc. (et cetera)
• M.P. (Member of Parliament)

3. Do not use full stops with contractions (in a contraction the last letter of the word and of the contraction are the same):

• Ltd (Limited)
• Dr (Doctor)
• St (Saint)

The rule about abbreviations and contractions is not followed by everyone. Sometimes it is a question of style. The important thing is to be consistent.