Is there any difference between 'plaid' and 'tartan'?

Solution 1:

I don't know if this helps at all. I'm Scottish and live in Scotland, I would only use the word plaid if referring to the length of tartan that a piper wears over his shoulder when in formal dress. Yes, tartan is registered to surnames but we also have tartans named after places.

Solution 2:

Depends on who you're talking to, and the context.
If you held up a swatch of polka-dot fabric and a swatch of tartan, most people in the US would identify one as polka-dot, and the other as plaid.

If you were speaking to someone who had a better than average knowledge of patterns, they could probably (and would probably) identify the different plaids as, say, buffalo, madras, gingham, burberry and tartan.

Most plaid fabric that resembles tartan would probably be called "tartan", whether or not it was associated with a specific clan and regardless of the garment.