Synonyms for U (same or very similar meaning)
WordNet sense 1 (a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine):
uracil
WordNet sense 2 (a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons):
uranium
WordNet sense 3 (the 21st letter of the Roman alphabet):
letter u
WordNet sense 4 (occupying the highest socioeconomic position in a society):
upper-class
From the ODE community, based on WordNet
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