Fungi is the plural for the word fungus, which is the term for eukaryotic organisms such as mushrooms, yeasts and molds.
The words fungus and fungi derive from the Latin word
fungus, which means "mushroom". In fact, in many Romance languages, the word of Latin derivation is used specifically to indicate mushrooms, for example "fungo" in Italian the singular for mushroom and "funghi" is the plural.
While the pronunciation of fungus is the same in both American and British English, the pronunciation of fungi varies. In the US, fungi is pronounced as
fun-guy, where the "i" at the end of fungi is pronounced like you would say the letter "i". In both cases, "g" is pronounced as a hard "g". That is to say, using the sound of the letter "g" as in the word "get" rather than pronouncing a "j" sound. Instead, the
British pronunciation of fungi is slightly different.