A commuter pass (定期券 teikiken) is a pass where you pay a fixed price for one or three or six months and you can get unlimited travel between two stations and only between those two stations. The longer you buy the pass for the cheaper per month the pass is. If you going between the same two stations regularly then it would be worth it to get a commuter pass. The commuter passes start 13 days after you purchase it.
How much a commuter pass is depends on the length of travel and the amount of months it is for. To check on this go to hyperdia.com/en and input your starting and ending stations and then in then top right-hand area of each of the routes there will be the cost for all of the commuter passes for that route.
To get a commuter pass you will need to go a green ticket buying machine, it will be alongside the other ticket buying machines. You will need to buy the commuter pass in Japanese there is no English version. You have to buy the commuter pass at the green ticket window (みどりの窓口 midori no madoguchi) if you already have an ICOCA card that you would like to use for the ICOCA card with a commuter pass. If you want an ICOCA card with a commuter pass and you do not have one then you will need to pay 500 yen for the ICOCA card deposit.
How to use the green ticket machine
Click the “定期券” button on the machine. You will have to choice getting an commuter pass or getting an ICOCA card with a commuter pass. You have to chose that you are buying a new pass “新規定期券” not continuing a pass. Then enter your information including birthday, phone number, how long the commuter pass will be for (1, 3, or 6 months), and starting and ending stations. Then you can pay by credit card or cash. Then confirm and you get your commuter pass.
How to buy from the green ticket window
For this you first have to get a commuter pass form (定期券購入申込書 teikiken kounyuu moushikomisho) and fill it in then you will take that to the green ticket window and follow the directions of the staff. If you already have an ICOCA card you would like to use for the commuter pass then use this method.