a thin rectangular shape paper or plastic material a flap to close the envelope adhesive or a string to secure the flap an address label a stamp or postmark a return address printed on the back
envelope which is a thin rectangular shape envelope which has paper or plastic material envelope which is a flap to close the envelope envelope which is adhesive or a string to secure the flap envelope which is an address label envelope which is a stamp or postmark envelope which is a return address printed on the back