以下 (yǐ xià) literally combines 以 (yǐ, 'by' or 'with') and 下 (xià, 'below' or 'under'), forming a compound meaning 'below', 'under', or 'less than'. As a preposition, it introduces content that follows — like items listed after a heading, text appearing later in a document, or conditions stated afterward. It's frequently used in formal writing, instructions, emails, and official documents to refer to what comes next.

As a noun, 以下 means 'the following [things]' — for example, 'the following points' or 'the items below'. It often appears with classifiers (e.g., 以下内容, 以下人员). Unlike English 'below', 以下 rarely refers to physical position; it’s almost always abstract or textual. It can also express quantity limits: 30岁以下 means 'under 30 years old', where it functions like 'less than' with numbers and measures.