The words moo, moue, mu sound the same but have different meanings and spellings. Why do moo, moue, mu sound the same even though they are completely different words?
The answer is simple: moo, moue, mu are homophones of the English language.
To emit the deep, bellowing sound made by a cow; low.
The lowing of a cow or a similar sound.
An obsolete form of <internalXref urlencoded="mo">mo</internalXref>.
To utter the characteristic cry of a cow; low.
A small grimace; a pout.
a disdainful grimace
The 12th letter of the Greek alphabet.
The Greek letter M. <bt>μ (μῦ</bt>, earlier <bt>μῶ)</bt>, corresponding to the English <em>M, m.</em> See <internalXref urlencoded="M">M</internalXref> and <internalXref urlencoded="mem">mem</internalXref>.
The Greek letter <bt>μ</bt>, corresponding to the English <em>masculine</em>
The 12th letter of the Greek alphabet (μ, Μ).
Definitions from The American Heritage® Dictionary of the English Language, 5th Edition., from The Century Dictionary., from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved., from the GNU version of the Collaborative International Dictionary of English. and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").