Perihelia is the plural form of perihelion, a scientific term used to describe the point in an object's orbit that is closest to the sun. While there may not be many direct synonyms for perihelia, related words can describe a similar concept. "Aphelion" is the opposite of perihelion, describing the point farthest from the sun in an object's orbit. Another term, "periastron," can refer to the point in an object's orbit closest to another celestial body, such as a star. Overall, these terms all describe specific points in an object's orbit and can help scientists understand its movement and characteristics.