The words ceil, seal, seel sound the same but have different meanings and spellings. Why do ceil, seal, seel sound the same even though they are completely different words?
The answer is simple: ceil, seal, seel are homophones of the English language.
To provide or cover with a ceiling.
Nautical To provide (a ship) with interior planking or lining.
A die or signet having a raised or incised emblem used to stamp an impression on a receptive substance such as wax or lead.
The impression so made.
The design or emblem itself, belonging exclusively to the user: a monarch's seal.
A small disk or wafer of wax, lead, or paper bearing such an imprint and affixed to a document to prove authenticity or to secure it.
To stitch closed the eyes of (a falcon).
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.