In general, do not use periods with acronyms or abbreviations. Use periods with the following abbreviations:
Abbreviation |
Notes |
in. |
This is used for inch. Always use a period at the end of this abbreviation. |
no. |
This is used for number. Always use a period at the end of this abbreviation. |
a.m. |
Use a.m. for the morning and p.m. for the afternoon. Using periods is preferred, but it is still acceptable to write this without periods if you do so consistently. |
p.m. |
