A backache is a pain or discomfort in your lower back.
You get backaches from all sorts of things - too much heavy lifting at work, slouching on the couch for hours, even sleeping wrong. Sometimes you can pinpoint what started it - like that time you moved some really heavy boxes or went to lift something without bending properly. But other times, it just seems to come out of nowhere. When someone says they have a backache, they're usually talking about this kind of pain, but if they say they have a kidney ache, the source might be somewhere else - although both are often related and can cause similar discomfort.
Any pain or ache in the back.
