periods

Periods are used in some abbreviations (e.g., i.e., a.m., p.m.) and not in others (ac, dc, rpm). Most acronyms do not have periods. When you end a sentence with "etc." (although this is seldom necessary) or another abbreviation that already includes a period, do not add another one.

This paper describes the program's purpose, objectives, schedule of deliverables, etc.
(Better: This paper describes the program's purpose, objectives, and schedule of deliverables.)

Subject:

Punctuation