The words call, caul, col sound the same but have different meanings and spellings. Why do call, caul, col sound the same even though they are completely different words?
The answer is simple: call, caul, col are homophones of the English language.
To say in a loud voice; announce: called my name from across the street; calling out numbers.
To demand or ask for the presence of: called the children to dinner; call the police.
To demand or ask for a meeting of; convene or convoke: call the legislature into session.
To order or request to undertake a particular activity or work; summon: She was called for jury duty. He was called to the priesthood.
A portion of the amnion, especially when it covers the head of a fetus at birth. Also called pileus.
See greater omentum.
A pass between two mountain peaks or a gap in a ridge.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition 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").