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lessen

/ˈlesən//ˈlesən/·verb
make something smaller in amount, degree, or intensity
Fig. 1 — I watch someone on a bench crying hard — sad-browed, tears running, a grey heaviness sitting thick over their head — while the person pressed close beside them keeps an arm around their shoulders, patting slow and steady.
01Definition

To lessen something is to make it smaller in amount, degree, or intensity — the plain, neutral 'make less'. You lessen the risk, the impact, the pain, the chance of failure: a measurable quantity simply goes down. It is the most everyday and least dramatic member of its family. Unlike mitigate, which counters or cushions a harmful effect, and unlike ease, which gently soothes something felt, lessen just reduces how much of something there is. It can also be intransitive — over time the pressure lessened on its own.

02In use
  • iWearing a helmet does not remove the danger, but it does lessen the risk of serious injury.
  • iiThe new bypass should lessen the volume of traffic passing through the town centre.
  • iiiNothing could lessen her determination to finish the race.
03Collocations
  • lessen the risk
  • lessen the impact
  • lessen the pain
  • lessen the burden
  • greatly lessen
  • lessen the likelihood

Family lessening (noun)

04Relations

=reduce, diminish, lower, ease, mitigate

≠increase, heighten, aggravate, intensify

05Compared
PairThe difference
lessen vs abatea hostile force dies down by itself (storm, uproar) → abate; an amount or degree gets smaller (risk, impact) → lessen.
lessen vs aggravatean outside hand forces the level up → aggravate; the level is brought (or comes) down → lessen.
lessen vs alleviateeases what someone suffers (pain, poverty) → alleviate; makes an amount or degree smaller (risk, impact) → lessen.
lessen vs diminishformal reduction of magnitude — or making someone seem smaller → diminish; plain, everyday easing of a felt amount → lessen.
lessen vs easeloosens how it feels (tension, pressure) → ease; shrinks how much there is (risk, impact) → lessen.

Also compared with exacerbate, mitigate, relieve, worsen

06TOEFL & IELTS

A reliable, neutral verb for reduction, especially with abstract nouns: 'lessen the risk', 'lessen the impact', 'lessen the likelihood'. It is a workhorse in problem-solution and cause-effect writing, where a measure lessens a danger or a drawback. Keep it apart from its near-neighbours: lessen is the plain 'make less' of an amount, mitigate is to counter or limit a harmful effect (often preventively), and ease is to soothe something gradually. Lessen works both transitively (the policy lessened poverty) and intransitively (the pain lessened).

07Asked
Are lessen and lesson the same word?
No — they are perfect homophones, both /ˈlesən/, and different parts of speech. Lessen is a verb, 'make or become less': the drug lessens pain. Lesson is a noun: a unit of teaching, or the wisdom an experience leaves behind. Spelling is the only visible difference, so the -en / -on ending carries the entire meaning.
Is it 'lesson learned' or 'lessen learned'?
Lesson learned — the noun; you learn a lesson, and nothing is being made smaller. The reverse trap ('this will lesson the risk') is just as common in exam scripts. A structural check beats memory here: -en is English's verb-making suffix, so lessen sits beside weaken, soften, deepen and shorten — all verbs built the same way.
Is lessen interchangeable with mitigate?
Only sometimes: lessen plainly shrinks an amount, whereas mitigate counters the harmfulness of a thing — the full separation, scene against scene, is on the lessen vs mitigate page in the 'Compared' list above.
When should you use lessen instead of reduce?
Reduce is the wider, more measurable word — you reduce a number, a price, a dose, often by a stated amount. Lessen prefers intensities you feel more than count: pain, risk, impact, anxiety. 'Reduce emissions by 40%' works; 'lessen emissions by 40%' sounds off, because lessen resists exact figures. When either fits, reduce is the more common, more technical choice.
Does lessen remove a problem or only shrink it?
Only shrink it — lessen never promises zero; the danger, pain or doubt survives at a lower level. The scene above is exact about this: all that patient consoling on the bench lightens the sorrow without ever emptying the bench of it — a trace of grey still hangs there at the end. When you need the stronger claim, reach for eliminate or remove instead.
Is lessen a formal or informal word?
Neutral, and older than it looks — lessen has been in continuous use since Middle English, which is why it fits both conversation and academic prose. In essays it does honest work with abstract objects: lessen the burden, lessen the likelihood. There is no adverb (no 'lessenly'), and the noun lessening is rare, so writers usually switch to reduction.