Luminometer is a scientific instrument used to measure light intensity. There are several synonyms for the word luminometer that can be used depending on the context. Some of the synonyms include radiometer, photometer, spectrophotometer, and fluorometer. A radiometer measures electromagnetic radiation, including light, whereas a photometer measures the intensity of light. A spectrophotometer is used to measure the amount of light absorbed or transmitted by a substance, while a fluorometer measures the intensity of fluorescence produced by a substance. These synonyms are often used interchangeably, but it's important to understand the differences between them to ensure accurate measurements in various applications.