foci

Usage notes
Both the "hard C" and "soft C" pronunciations are accepted. Although focus has C followed by a non-frontal vowel and is thus universally pronounced with a "hard C", there is a grey area for pronouncing the plural form foci. Under normal orthography rules, the C should be transmuted due to it being followed by one of the three frontal vowels (e, i, and y), but the "hard C" pronunciation is also valid due to this word being the plural of a word that is strictly pronounced with a hard C.

Etymology
.  (the  changed to ).

Noun

 * 1)  soccer