I am not an attorney but I'd say that mitigate means to not allow any more bad things to happen than necessary.

IE if a tenant moves out early on me with six months left on a lease it is my oblgation to mitigate my loss by renting it to someone else if possible and letting the first tenant off for only the months he occupied it plus the vacant time.

Often to encourage this to happen I'll ask the first tenant to kick in 50 or 100 a month to incentivize the new tenant to rent.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.