The frame of the glasses has arms and lens-holders/placement. The arms are held on by screws, which you can see in the hinges (joints) of the glasses

Perhaps the middle part is called the 'bridge' as it bridges or joins the 2 halves. Under the bridge the parts that rest on our noses could be called 'nose rests', but I am not sure. If I break them when overseas, I will simply say "this part - broken" and the other person will probably tell me what the parts are called. That is my language strategy. )))