In this work, we conducted extensive electrical characterization on the endurance degradation in silicon n-channel ferroelectric FET (FeFET) and provide insights into the physical processes of degradation. We discovered distinct behaviors of FeFETs compared with conventional high-k MOSFET due to the interaction between polarization switching and charge trapping. We demonstrate that: i) the higher the constant voltage stress, the less the degradation due to compensation of trapped electrons with polarization switching; ii) breaking the constant voltage stress into a sequence of pulses with inter-pulse delay causes degradation with longer delay, similar to bipolar cycling, due to partial polarization switching.