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)

• cocoa butter
• cocoa butters
• cocoa fat
• cocoa nibs
• cocoanut
• cocoanuts
• cocoas
• cocoa-wood
• co-codamol
• co-codamols
• coco-de-mer
• coco fibre
• COCOM
• CoCom
• coconscious
• coconsciouses
• coconsciousness
• coconsciousnesses
• coconut
• coconut butter
• coconut crab
• coconut crabs
• coconut ice
• coconut ices
• coconut matting