"Be in demand" means to be desired or required by people. There are many other words that describe this concept, such as popular, sought-after, coveted, and trendy. When something is popular, it means that it is widely liked or admired by people. Sought-after refers to something that is desired or wanted by many people. Coveted is a word that describes something that is eagerly desired or coveted by others. Lastly, trendy refers to something that is fashionable or currently popular. All these words can be used interchangeably with "be in demand" to convey the same meaning.