by which

که به استناد به آن، گه با درنظر گرفتن آن

که از طریق آن

که توسط آن

E. g
A lead is also the amount or distance by which someone is in front

که بموجب آن

By which : که توسط آن_که از طریق آن

مثال:

The methods by which the height of waves was being measured those days generated
inaccurate data
معنی: روش هایی که توسط آن ارتفاع موج ها داشت اندازه گیری میشد، در آن روزها اطلاعات نادرستی را تولید کرد

They were hiring a taxi by which they would be able to go back to their house اونا داشتن یه تاکسی راکرایه میکردن ( که بوسیله آن ) قادر باشن به خانه شان برگردن

wherewith