应用 (yìng yòng) functions both as a noun meaning 'application'—especially in technical or practical contexts—and as a verb meaning 'to apply' or 'to put into use'. The character 应 (yìng) conveys responsiveness, suitability, or fitting a situation, while 用 (yòng) means 'to use' or 'usage'. Together, they express the idea of using something appropriately in a real-world context, such as applying knowledge, theory, or software. It’s commonly used in academic, technological, and professional settings.

As a noun, 应用 often appears in compound terms like 应用程序 (yìng yòng chéng xù, 'application program') or 实际应用 (shí jì yìng yòng, 'practical application'). As a verb, it typically follows a subject and object and may take aspect particles like 了 or 过 (e.g., 已经应用了). It carries a formal or neutral register and is rarely used in casual spoken Chinese for simple everyday actions—those are more often expressed with 用 or 使用.