From JB:

"Q&A
What’s the difference between the E190 and a Regional Jet?
Good question. This is a very gray area even among aviation experts, partly because the definition of a regional jet is vague. The most commonly used regional jets are CRJs and ERJs with 50 to 85 seats. If you compare the E190 to other aircraft, it actually looks closer, in terms of seats, to the 737-500 and 737-600 operated by major carriers. The standard definition, which is nearly universal in the aviation community, is that the E190 is a mainline jet. But when it really comes down to it, the E190 is truly in a class of its own."

I saw a 190 taxi past a CRJ last week. No *******ing way that's an RJ.