Let's start with a quote about writing:
"Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that every word tell."
- William Strunk, Jr., Elements of Style
Pleonasm is the use of more words than those necessary to denote mere sense. Redundancies are found everywhere. Advertisers are particularly guilty of this when promoting their offers: "an added bonus" or "a free gift."
In your writing it is always a good practice to review the completed document with an eye toward avoiding saying the same thing twice. The use of redundant phrases in your writing is a habit worth breaking.
Here is a short list of some to look out for:
|consensus of opinion||consensus|
|each and every||each or every|
|exactly the same||the same|
|he/she is a person who||he/she|
|in spite of the fact that||although|
|job functions||job or functions|
|one and the same||the same|
|and also||and or also|
Note: Some redundancies contained in phrases have been legitimized over time and should be left alone: safe haven, hot water heater, new beginning, tuna fish, never before, joined together, and false pretenses.
Sources: Common Errors in English by Paul Brians; Merriam-Webster's Eleventh Collegiate Dictionary; the Internet