Quote Originally Posted by Mike S
One quip, and I know you are aware of the difference Alan but some newbies might not be:
A PLAID is a garment you wear pinned to the shoulder.
TARTAN is the sett design material it, and kilts, are most often made of.
Sorry, just a pet peeve of mine.
Alan wasn't completely wrong...
http://www.m-w.com/dictionary/plaid
Function: noun
Etymology: Scottish Gaelic plaide
1 : a rectangular length of tartan worn over the left shoulder as part of the Scottish national costume
2 a : a twilled woolen fabric with a tartan pattern b : a fabric with a pattern of tartan or an imitation of tartan
3 a : TARTAN 1 b : a pattern of unevenly spaced repeated stripes crossing at right angles
"Plaid" has several correct definitions.

-ian