An API refers to a chemical substance used to manufacture pharmaceutical products, typically obtained through chemical synthesis or natural extraction. APIs are the foundation of pharmaceutical manufacturing and are a crucial factor in determining the quality and efficacy of the drugs. APIs usually have specified chemical structures and purity requirements, therefore, the quality control and standard requirements for APIs are relatively high.

Intermediates, on the other hand, are chemical substances used in the synthesis of APIs during the pharmaceutical manufacturing process. They are typically intermediate products obtained through multiple chemical reaction steps. Although intermediates themselves usually do not possess pharmacological activity, they play a significant role in pharmaceutical manufacturing, influencing the synthesis efficiency, quality, and cost of APIs, among other factors. Intermediates generally need to meet certain purity and chemical structure requirements to ensure the quality and efficacy of the API.

Therefore, the difference between intermediates and APIs lies in their role: intermediates are chemical substances used to manufacture APIs, while APIs are ultimately used to manufacture pharmaceutical products. Intermediates play a critical role in the pharmaceutical manufacturing process, while APIs are a key factor in the quality and efficacy of the finished product.