<s>[INST] You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise. Question:  What is the concept of social stratification in sociology? Context: In sociology, social stratification is the ranking of people in a society in a hierarchy based on various criteria. Answer: [/INST]Social stratification refers to a system by which a society ranks categories of people in a hierarchy.</s>