Battery or starter trouble?

My wife Honda accord hesitated to start a couple
of weeks ago, but started.... I drove it last week it
did the same one day, but started normally the
other days. Then another day I drove it to work with
no problems that morning,  but later that day when
I got off  I tried to start it up ,it tried to turn over but
very weakly and didn't start. Now it does nothing
when I turn the ignition.... no crank, no clicks or
anything,  but the headlight, radio, windows still
work. What could be the cause