The signal comes in the form of molecules which we're going to call throughout the lecture here 'ligands'.

信号通常以分子的形式来传递,在这门课里我们把这种分子叫做配体

耶鲁公开课 - 生物医学工程探索课程节选

In the case of a ligand-receptor, a chemical signal in the form of a concentration of ligand gets converted into a biochemical signal.

在配体-受体系统中,配体浓度这种化学信号,转化为生化信号

耶鲁公开课 - 生物医学工程探索课程节选