Amelioration, also called semantic elevation or melioration, is the process by which a word acquires a more positive evaluative meaning over time. The term derives from Latin melior "better." Amelioration is the affective counterpart of pejoration and the rarer of the two directions in the documented record of semantic change.
Amelioration typically proceeds through one of two routes. In the first, a word habitually applied in admirable or prestigious contexts absorbs the positive loading of those contexts as part of its meaning. In the second, hyperbolic or ironic use of a strongly negative word loses force through repetition and is reanalysed as a positive intensifier. The latter pathway accounts for several of the most striking English examples.
A subset of ameliorations involves intensifiers originally drawn from negative or fear-based vocabulary. Awesome, terrific, tremendous, fantastic, incredible all originally described overwhelming or fearful experiences. Repeated hyperbolic use leached the negative content and left a generic positive intensifier. Crystal (2003) notes that this pattern recurs in many languages and is often associated with adolescent and youth speech, which generates novel intensifiers as older ones lose force.
Cross-linguistic surveys consistently report fewer ameliorations than pejorations. Several explanations have been proposed. Negative evaluation tends to be more salient cognitively and pragmatically, recruiting words into critical use more readily than into praise. The euphemism treadmill (see Pejoration) constantly drags polite vocabulary downward. Positive intensifiers wear out and need replacement, but the older positive items typically fall out of use rather than reverse direction. Ullmann (1962) and Hock (1991) treat the asymmetry as a stable feature of historical semantics rather than a bias of the documentary record.
Amelioration concerns connotation; broadening concerns extension. The two can co-occur (nice both ameliorated and broadened), but the analytical distinction matters: a word can ameliorate without changing its referential range (knight still refers to a single social role) and can broaden without changing connotation (thing broadened from "assembly" to "any entity" without affective loading).
For learners, amelioration matters mainly through fixed expressions and historical readings. A pretty penny preserves the older "considerable, sizeable" sense; a fond hope preserves "foolishly optimistic." In Shakespeare and the King James Bible, nice often means "fastidious" or "subtle" rather than "kind," and pretty may mean "cunning."
The hyperbolic class (awesome, terrific, fantastic, incredible) is also worth flagging in vocabulary teaching. These items are now decorative intensifiers, not literal claims, and learners who use them at full etymological strength sound oddly emphatic.