Flew - flu - flue

These are three homophones that can cause spelling problems. They all have a long vowel like that in 'too', 'shoe' or 'who'.

• Flew is the past tense form of the irregular verb 'to fly'.
• Flu is an illness. (The word is an informal shortening of the original name, 'influenza'. This was an Italian word for an epidemic of any disease ('under the influence of the stars'). From 1743 it was applied specifically to the [family of] ailments that we now call flu, although we no longer normally write the apostrophe to indicate contraction, which was regarded as 'correct' well into the twentieth century: 'flu.)
• A flue is a pipe for gases, originally for waste gases, especially those from a fire. So a flue was another word for a chimney. It became used mostly for the duct or pipe inside a chimney: the word chimney became the solid stack and the flue became the hollow pipe. Subsequently, importantly with the development of steam technology, the word flue became used for any pipe or duct being used to convey heat, as in a boiler for a steam railway engine, or a ship.
  • • flue is also an obsolete spelling of flu.

For a foolish children's rhyme that may amuse you , go to flea - fly - flew - flue.