夹层

例句：

1. 1. The sandwich has three layers: bread, mayonnaise, and cheese.
   这个三明治有三层：面包、芥末和奶酪。
2. 2. The book is divided into several sections with different levels of complexity.
   这本书被分成了几个部分，每个部分的复杂程度不同。
3. 3. The construction used a layered approach to ensure stability.
   施工采用了分层方法来确保稳定性。