How A Class Is Structured
While Aikido classes may greatly vary from instructor to instructor the elements and structure of classes are similar even for special events. This means that when visiting another dojo you should know what to expect. This is a typical class:

The sensei (先生, teacher) starts the class usually with a clap and the gakusei (学生, students) sit in a row in grade order right to left. Sensei takes the rei (礼, bow) first to the kamiza then to the students. The gakusei follow both bows (when bowing to the sensei the gakusei say “onegaishimasu"). The gakusei then follow instructions the sensei and copy them.
A class usually starts with communal warm-ups called Junbi-Taiso (準備-体操, Preparation Exercises) it is important to do this to make sure everybody is sufficiently ready for the class and to promote a communal spirit.
This consists of both dynamic and static stretches including Tekubi-Kansetsu Junan Undo (手首関節柔軟運動, wrist stretching exercises), with an emphasis on Aikido. And Makko-Ho (真向法) stretches.
Also it is common to do meditation (瞑想), Misogi (禊), and zazen (座禅) exercises to get a good flow of oxygen into the body and to clear the mind.
Commonly warm-ups are followed by Fundamental movement exercises called Kihon Dosa (基本 動作) and Body motions called tai subaki (体捌き). These practices strengthen posture and improve speed of movement, flexibility and agility. These usually include ground level movements from seiza such as shikko (膝行).
Another common set of exercises are rolling, falling and ukemi (受身), this is a means of strengthening basics and the foundations of Aikido. It helps a person learn to move and follow a technique with flexibility and fluidity such as to reduce harm during a technique.
The lesson is conducted by the sensei showing an exercise or a technique while the gakusei sit patiently and watch in seiza (正座). When the demonstration is finished the sensei will tell the gakusei to practice and they will do so attempting to copy exactly what has been shown.
The sensei may stop the class at intervals but saying yame (止め, stop) or clapping and demonstrate again, the class sits in seiza and watches, or Kotae (答え, answer/ change over) meaning change over in which case people will swap partners. At other times the sensei will ask the class to follow and copy them and at other times the class may practice as a group, this all depends on the activity and what is being taught.
The class usually ends with warm down exercises then the gakusei line up in seiza in grade order once again. The class is then closed by the rei being taken as described above. At the end of the class notices and announcements are given.
The sensei then bows and leaves the mat. The most senior grade then says “dojo ne rei” and the class bows and disperse. It is good manners for students to bow to each other as a sign of thanks and respect, remember this is an important piece of your practice, it is also customary to thank the sensei.