Comparison of adjectives (and adverbs) is a grammatical category that has passed practically unremarked upon by generations of Latin linguists. Latin grammar books (with few exceptions, cf.
Pinkster 2005: 47; K ühner - Holzweissig 1912: 565-566) omit entirely the question of which adjectives can be compared and which cannot. Nevertheless, the data from modern languages show that the category of comparison of adjectives (and adverbs) is actually highly limited, making it essential to address this question for Latin, too.
One of the issues comprehended within the extremely complex area of (non-)gradability of adjectives is periphrastic comparison. Latin grammar books explain, based on the assertions of ancient Latin grammarians, that it applies to adjectives ending in -eus, -ius and -uus, implying, or even explicitly stating, that the reason for this type of comparison is phonetic incompatibility of the word-formative suffix with the comparative suffix.
However, two facts call for reinterpretation of the matter: 1) periphrastic comparison also occurs in other adjectives for which there is no phonetic incompatibility; 2) by contrast, some adjectives in -eus, -ius and -uus actually do have simple forms. In the light of these facts, this paper aims to map the real situation of periphrastic comparison in Latin.
The employed corpus comprises all the words marked as adjectives in the Oxford Latin Dictionary (more than 10,000 items) and all their occurrences throughout the database Bibliotheca Teubneriana Latina III.