Exahertz is a unit of measurement used to describe the frequency of electromagnetic waves. It represents one quintillion hertz or 10^18 hertz. While there may not be many synonyms specifically for exahertz, there are other units of measurement used to describe similar frequencies. One example is petahertz, which is one thousand trillion hertz or 10^15 hertz. Other units of measurement in this range include terahertz, gigahertz, and megahertz. These units are commonly used in various fields such as telecommunications, electronics, and physics research. Despite the lack of specific synonyms, understanding the relationships between different units of measurement is crucial in these fields.