The Official Tweed Appreciation Thread

[BlueSteel]

Fox Char-Navy Herringbone Tweed in a sportcoat from Spier & Mackay:

 

[J.A.G]

I have a serious question about tweed - namely, when is a wool jacket a tweed jacket, and what is the difference? These are the putative tweeds in my closet. The four on the right I know to be tweed, because they have a “Harris Tweed” label in them. But what about the brown windowpane jacket on the left? I found it in an online search of the Andover shop, and it was the only jacket in my size in the store. So I picked it up the next time I was driving by, less than a year ago.

All wool, but not as coarse as the Harris Tweeds. So is this properly called a ”tweed”, and if so, why?