Similar words
gemelo
gemelo specifically means an identical twin; mellizo specifically means a fraternal twin — a precise, useful distinction.
Similar in other languages
French
jumeau
jumeau is the French word for the same thing — both mean "twin."
Portuguese
gêmeo
gêmeo is the Portuguese word for the same thing — both mean "twin."
Practice
1 What does mellizo mean?
twin
2 Fill the gap: Es ___ de mi primo.
Full sentence: Es mellizo de mi primo. (He is my cousin's twin.)
3 Which fingerprint chart matches mellizo?
mellizo: neutral register, common frequency, general domain, neutral connotation.