Noun lessening has 1 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"
    --1 is a kind of change, alteration, modification
    --1 has particulars:
     shrinking, shrinkage; casualty; sinking; attrition; dwindling, dwindling away; waning
,Verb lessen has 3 senses
  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 fall to under a hundred pounds"; "his voice fell to a whisper"
    --1 is one way to change magnitude
    Sample sentence:
    Something ----s
  2. decrease, lessen, minify - make smaller; "He decreased his staff"
    --2 is one way to change, alter, modify
    Sample sentences:
    Somebody ----s something
    Something ----s something
  3. subside, lessen - wear off or die down; "The pain subsided"
    --3 is one way to weaken
    Sample sentence:
    Something ----s