介子

Mesons were predicted in 1935 by Japanese physicist Hideki Yukawa (汤川秀树) as the carriers of the strong nuclear force, and the first one (the pion) was confirmed in cosmic rays in 1947. Yukawa won the 1949 Nobel for the prediction. The Chinese term mirrors the Greek 'meson' = 'middle one' — heavier than electrons, lighter than protons.

介 (jiè) means 'between / intermediate' — a perfect calque of Greek mesos 'middle.' 子 (zǐ) is the standard particle-physics suffix (电子 diànzǐ 'electron,' 质子 zhìzǐ 'proton,' 中子 zhōngzǐ 'neutron'). So 介子 = 'in-between particle.'