The inflation break-even is the difference in yield between a conventional bond (coupon rate) and its inflation-linked (real rate) equivalent (the same issuer, same maturity ...) :

Over a given period, if observed inflation exceeds the break-even (expected inflation), the inflation-linked bond will generate more returns than its conventional counterpart.

Back on the dynamics of break-even in 2010

The year 2010 was characterized by the crisis of European sovereign debt in the spring which resulted in a significant decline in inflation expectations that had just recovered from their level before the financial crisis. Between May 2010 and August 2010, 10 years inflation expectations lost 60 basis points in euro area and 75 in the U.S before bouncing back in the fall after the announcement of bailout plans .