plane, plain

The words plane, plain sound the same but have different meanings and spellings. Why do plane, plain sound the same even though they are completely different words?

The answer is simple: plane, plain are homophones of the English language.

plain
  1. :: adjective

    Free from obstructions; open; clear: in plain view.

  2. :: adjective

    Obvious to the mind; evident: make one's intention plain. See Synonyms at apparent.

  3. :: adjective

    Not elaborate or complicated; simple: plain food.

  4. :: adjective

    Straightforward; frank or candid: plain talk.

plane
  1. :: noun

    Mathematics A surface containing all the straight lines that connect any two points on it.

  2. :: noun

    A flat or level surface.

  3. :: noun

    A level of development, existence, or achievement: scholarship on a high plane.

  4. :: noun

    An airplane or hydroplane.

Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.

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About Homophones

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").