how long - usually refers to length, but can refer to the amount of time you have to wait. Example, "How long is a that rope ?", "How long do I have to wait to see the doctor ?" how soon - refers to the time until some event. Example. How soon before dinner is ready ? How often - refers to the frequency with which an event occurs. "How often do I need to take the medicine ?" Answer: " 3 times each day, with meals !" ( 3 times per day) "How often do you come here?" Answer: "Every Tuesday!" (once per week) A.

These are three very different words. I am sure the dictionary will give you the answers you need.