DESCENDING COMPARISON

271. The change in form of adjectives in the positive, comparative and superlative shows that one object has more of a quality than others with which it is compared. But we also wish at times to express the fact that one object has less of the quality than is possessed by others with which it is compared; so we have what we may call the descending comparison, by means of phrases formed by using less and least instead of more and most. Using less with the positive degree means a degree less than the positive, while using least expresses the lowest degree. For example:

Descending Comparison
Positive Comparative Superlative
beautiful less beautiful least beautiful
intelligent less intelligent least intelligent
sensitive less sensitive least sensitive
thankful less thankful least thankful