同位素

isotope

like / same / similar / together / alike / with

see 衚衕|胡同[hu2 tong4]

par

position / location / place / seat / classifier for people (honorific) / classifier for binary bits (e.g. 十六位 16-bit or 2 bytes) / (physics) potential

raw silk / white / plain, unadorned / vegetarian (food) / essence / nature / element / constituent / usually / always / ever

fertile isotope

isotopic separation

radioactive isotope / radioisotope

fissile isotope