flue
(a pipe or channel that takes smoke, gas, etc. out of a building)
- We need to install a metal flue for the furnace.
- The smoke won’t go out because the flue is blocked up.
flu [formal: influenza]
(an illness like a very bad cold that causes fever, pain, and weakness)
- I think I have got the flu.
- She was in bed with flu for a week.