Full Term??

Julia
I'm only 35 Weeks, which is why I'm so confused. I had an ultrasound to see how my little man is doing in there yesterday and the tech said he's itty bitty. She estimates 4 lbs (which I know they can be super inaccurate, she said even at that size they aren't concerned because I'm itty bitty) what confuses me is she said, "You're full term!" 
I thought 40 weeks was full term, 37 at the earliest.