Comparison involves morphology and syntax for describing something as ranking above or below something else, as being equivalent to something, or as falling at the very top or the very bottom of the scale. Many adjectives do this by inflecting for grade, having plain, comparative and superlative forms. This inflectional system applies also to a small number of determinatives and adverbs. Others are modified by ‘more’ or ‘less’.

Superlatives express set comparison, with one item outranking all of the others. The comparative form, by contrast, is predominantly used in term comparison – comparison between a primary term and a secondary term. There are also comparisons of equality, which are always marked by a modifying phrase rather than by inflection, along with a type of non-scalar comparison where the issue is simply of identity or similarity.

The prepositions ‘than’ and ‘as’ often license as complements a distinctive type of subordinate clause called a comparative clause. Comparative clauses constitute one of the three major kinds of tensed subordinate clause, being distinctive in that they are obligatorily reduced in certain ways relative to the structure of main clauses.

The case study in this chapter aims to revise the way the comparison of adjectives is introduced pedagogically. The complex of rules which state that ‘one-syllable adjectives take “inflectional” (-er, -est) comparison, while three-syllable adjectives take “phrasal” (more, most) comparison’, followed by varying refinements of both for two-syllable adjectives, is challenged, on the basis of a corpus study of such forms. It is shown that several words break these ‘rules’, for example real, whose comparative form is almost always more real. Various factors are suggested as influencing the choice between the two options, in particular frequency: rare words are more likely (‘likelier’?) to take phrasal comparison. Suggestions for a revised rule are given, along with practical exercises. The chapter demonstrates the relevance of corpus analysis in devising appropriate advice for learners.