名词 “gesture、signal、sign” 和 “symbol” 都既可以用来表达具体的事物，也都有相应的衍生抽象含义，我们在接下来的节目中，先通过一段音频来为大家介绍这四个词语在表达看得见摸得着的事物时的含义，再逐个分析它们从这些含义中衍生出的抽象含义。

They used a sticky tape test to painlessly collect skin cell samples from the hands and backs of two-month-olds. They found detectable immune biomarker changes in the cells that appeared to be linked ...