'显影剂' (xiǎn yǐng jì) is a photographic chemical compound used to convert the latent (invisible) image on exposed film or photographic paper into a visible, stable image. The word breaks down literally as '显' (to reveal, make visible), '影' (image, shadow), and '剂' (agent, chemical substance). Together, they describe a substance whose specific function is to develop or bring out photographic images.

This term belongs to traditional analog photography terminology and appears in contexts like darkroom work, film processing labs, historical photography discussions, and medical imaging (e.g., X-ray film development). While largely replaced by digital workflows today, it remains essential in photography education, restoration of old photographs, and specialized scientific or artistic applications. It is not used for digital image editing software — those use algorithms, not chemical agents.