The abbreviation etc. (from the full form et cetera) came into English from the Latin expression et cetera (“and the rest”). Do not use etc. as a substitute for the adverb et al., which came into English from another Latin expression, et alii (“and others”).
Use etc. when you list some, or a few, of many items, as in We will discuss the Plymouth Colony, the Puritans, the witchcraft trials, etc., in our early American literature seminar. (Never write “and etc.” or “& etc.”, as these are redundant.)
Use et al. when you mention one person or a few people out of several or many, as in bibliographies, footnotes, or textual references: In the October issue of the medical journal, Smith, Jones, Roe, Doe, et al., [not etc.] discuss correct insertion of artificial airways.
<taken from Microsoft Encarta Dictionary>
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