The correct spelling of the word "cartmill" is /kɑːrtmɪl/. It is composed of two syllables: "cart" and "mill". The first syllable "cart" is spelled with the letters "c", "a", "r" and "t", and it is pronounced as /kɑːrt/. The second syllable "mill" is spelled with the letters "m", "i", "l" and "l", and it is pronounced as /mɪl/. The word "cartmill" refers to a device used to grind grain into flour. It is important to spell words correctly to avoid confusion and to effectively communicate with others.