Exercise 2 solution

Bight - a U-shaped curve; the rope does not cross itself.
Loop - the bight is closed by crossing the rope over itself, so there is a crossing point.
Turn - the rope goes once around the chair leg.
Round turn - the rope goes twice around the chair leg, so it touches the leg for a full circle plus more.

Any wording that distinguishes them by "crosses itself" and "once or twice around an object" is fine.