变故 [biàn gù]
unforeseen event
accident
mishap
misfortune
例句：1.生活中发生的重大变故往往是我们的第二次机会.
We all have big changes in our lives that are more or less a second chance.
扁骨 [biǎn gǔ]
{生理} flat bone
os planum
例句：1.骨可根据形状分类,有长骨、短骨、扁骨、不规则骨和含气骨.
Bones may be classified according to their shape.There are long bones,short bones,flat bones,irregular bones and pneumatic bones.