Historically the Adjective is a younger class of words as compared to the Noun. So it has borrowed many of its categories and inflections from the Noun and the Pronoun. The Adjective had the following categories: Gender: It still existed in OE but was the first category to disappear in the 11th c. Case: At the end of OE Period Instrumental Case fell together with Dative Case due to the homonymy of inflections (see the table below); All other cases disappeared by the end of the 13th c. also due to the homonymy of inflections (see the table below). System of Declensions: The system of declension was inherited from PG. Adjectives had two declensions that had to do also with the category of determination – strong (definite) and weak (indefinite) – and unlike nouns practically all adjectives could be declined both ways (by strong and weak declension). So an adjective did not belong to a particular declension, its declension depended on several factors. There were exceptions from the rule: some adjectives were declined always strong (eall (all), maniζ (many), ōþer (other)), others – always weak (ilca (same)). The endings of the adjectives showed the agreement between a noun and an adjective. There were a lot of homonymous forms à the distinction between the declensions faded in ME and the declensions disappeared as far as there was no necessity any more to keep them. Number: There were some homonymous forms in Singular and Plural in both declensions, so the category of Number disappeared together with the system of declensions. The Adjective lost many of its categories in ME as far as all the inflections were lost. Thus it became an unchangeable part of speech. In ME the following changes happened: 1) In most cases inflections -er, -est were used to form the comparative and the superlative degrees; 2) Root-sound interchange fell into disuse (l o ng – l o nger – l o ngest), though in some cases it was preserved as an exception from the rule (e.g. old – elder – eldest; far – further – furthest); 3)A new way of formation of the degrees of comparison appeared: more + Adj (comparative) || most + Adj (superlative). It was applicable to all adjectives and was interchangeable with -er, -est way of formation till 17th – 18th c. In NE, during the Normalisation Period, the modern rule appeared and this way was applicable only to a certain group of adjectives. In OE there were 3 ways of formation of degrees of comparison: 1)inflections, 2)root-sound interchange+inflections, 3)suppletion
In ME there are foll. changes: -er, -est were used to form compare & superl. Degrees. -root-sound interchange fell into disuse (long-longer-longest). Exeptions: old, far-furthe-furthest -new way of form-n: More, most + adj.
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