Rei Ho (礼法) Courtesy The Art Of Bowing
In Aikido tradition and etiquette are very important. The most basic form of this is the bow, this is likely the most often used activity in Aikido and is a sign of respect.
There are two forms of bow commonly used that of the standing bow立礼 (Ritsu Rei) and the sitting bow 座礼 (Za Rei). In both cases the back should be straight and and taken at a respectable distance. The deeper and longer the bow the higher the level of respect.
Bows are conducted throughout the class from the start, to the kamiza and the instructor. Between students while practising with each other, then at the end of the class.