Rainfly and Tent flap

Rainfly noun - Flap consisting of a piece of canvas that can be drawn back to provide entrance to a tent.

Tent flap is a synonym for rainfly. In some cases you can use "Tent flap" instead a noun "Rainfly".

Tent flap noun - Flap consisting of a piece of canvas that can be drawn back to provide entrance to a tent.

Rainfly is a synonym for tent flap. You can use "Rainfly" instead a noun phrase "Tent flap".