Metaplasia refers to the replacement of one mature cell type with another mature cell type: for example, squamous metaplasia of the respiratory columnar epithelium - as evidenced by the metaplastic cough of a smoker.

化生是指一种成熟细胞类型被另一种类型的成熟细胞替代。例如，呼吸柱状上皮的鳞状化生由吸烟者的化生咳嗽证明。