The term 'visible spectrum' refers to the range of electromagnetic radiation that can be detected by the human eye. There are several synonyms for this term including 'visible light', 'optical spectrum' and 'rainbow colors'. Other related terms include 'chromatic spectrum' and 'color spectrum'. These terms are often used interchangeably to describe the range of colors that can be seen by humans. The visible spectrum is just one small part of the larger electromagnetic spectrum, which includes many different types of radiation such as radio waves, microwaves, and X-rays. Understanding the visible spectrum is important in many fields including astronomy, physics, and optics.