"lessening" in the noun sense
1. decrease, lessening, drop-off
a change downward
"there was a decrease in his temperature as the fever subsided"
"there was a sharp drop-off in sales"
"lessening" in the verb sense
1. decrease, diminish, lessen, fall
decrease in size, extent, or range
"The amount of homework decreased towards the end of the semester"
"The cabin pressure fell dramatically"
"her weight fell to under a hundred pounds"
"his voice fell to a whisper"
2. decrease, lessen, minify
"He decreased his staff"
3. subside, lessen
wear off or die down
"The pain subsided"
Source: WordNet® (An amazing lexical database of English)
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