What part of speech is the word between?

It is very important to promote self esteem in young children

If you want to change from landscape orientation to portrait orientation, what would you do? turn the camera around. flip the camera over. turn the camera 90 degrees. turn the camera 360 degrees.

"the only completely stationary object in the room was an enormous couch on which two young women were buoyed up as though upon an anchored balloon. they were both in white and their dresses were rippling and fluttering as if they had just been blown back in after a short flight around the house."