Pi meson, also known as pion, is a subatomic particle consisting of one quark and one antiquark, with a very short lifetime. There are several synonyms for pi meson, including pi-meson, meson pi, p-charged meson, and Yukawa meson. These synonyms are often used interchangeably in scientific literature to describe this fundamental particle. The pion is important in particle physics as it was the first meson to be discovered and it continues to be studied as a probe to investigate strong interactions between subatomic particles. Its properties have also led to the development of other particles and theories in the field of particle physics.