The English language contains various two-letter words. Here is a list of such words. Some of these words are debatable, because they are archaic, slang, proper names, or words borrowed from other languages.
io – an interjection; (all the following are with initial capital) the daughter of Inachus in Greek mythology; also a moon of Jupiter; also an alternate spelling of Kiho; also a Hawaiian species of hawk
né – born with the name of (the male form of "née")
no – not any; also a general negative response; no. is also an abbreviation of the word "number"
nu – a letter in the Greek alphabet; also (with initial capital) the god of the ocean in Egyptian mythology; also (with initial capital) an ethnic minority in China
Ob – a river in Siberia (one of the largest rivers in the world)
re – second tone of the diatonic scale; also an alternative spelling of Ra
ri – a mythical creature said to be half human and half jellyfish
Ro – a constructed language of the "philosophical" type (words from similar categories begin with similar letters), invented by the Rev. Edward Powell Foster with his wife
si – a note in the diatonic scale; also (with initial capital) the god of the moon in Mochican mythology
so – to the amount or degree expressed or understood; also a question asking what logically follows from a statement; also fifth tone of the diatonic scale