diaeresis or dieresis /dī-ērˈi-sis or -erˈ/

1. A mark ( ¨ ) placed over a vowel, esp the second of two adjacent ones to show that it is to be pronounced separately, as in naïf
2. A pause or break where the end of the word coincides with the end of a foot (prosody)

• foen
• foes
• foetal
• foetal alcohol syndrome
• foeticidal
• foeticide
• foeticides
• foetid
• foetider
• foetidest
• foetidness
• foetidnesses
• foetor
• foetors
• foetoscopies
• foetoscopy
• foetus
• foetuses
• fog
• fogash
• fogashes
• fog bank
• fog banks
• fog-bell
• fog-bells