This very small category of abstract nouns contains words formed by attaching the suffix -itia to Latin adjectives. Whenever the English derivative has evolved in a normal and regular fashion, it will have an ending in -ice. However, there are perhaps as many exceptions to that rule as there are regular examples. Here are three that run true to form:
|L||malus (“bad”)||>||malitia (“badness”)||>||E||malice|
|justus (“righteous”)||>||justitia (“righteousness”)||>||justice|
|avarus (“greedy”)||>||avaritia (“greediness”)||>||avarice|
The historical reason for the -ice spelling is to be found in the confusion of -itia and -icia during the late Latin period (cf. §12 and see §14.3.b). Within the French language, Latin nouns that had ended in -itia could also evolve into forms in -esse. Accordingly, English has largess(e) < largitia < largus (“abundant,” “bountiful”) and caress < *caritia < carus (“dear). The word caress is closely related in form, if not in meaning, to charity (§45), since the hypothetical *caritia must have been a late Latin variant for caritas. But we have entered an exotic realm of historical morphology, and you certainly shouldn’t worry about remembering these unusual forms.