How to say "decrease" in Japanese

• 減るへるJLPT N3approx.Common
  godan verb, intransitive verbThe intransitive verb: use it when the thing itself decreases in size or number, with no agent mentioned — the amount, the number, or the level simply becomes smaller. For decreasing something, use the transitive 減らす.
  会員かいいんは５人にんに減へった。↗

  The number of members decreased to five.
• 減少げんしょうJLPT N1approx.Common
  suru verb, transitive verb, intransitive verb, no-adjectiveA noun for a decrease, reduction, or decline in an amount or number; the neutral choice for stating decreases as facts, typical of news reports and statistics such as a declining population or falling sales.
  あまりチームに頼たよりすぎると、個人こじんの闘争とうそう本能ほんのうが減少げんしょうするかもしれない。↗

  When you rely on the team too much, it may reduce your individual competitive instincts.
• ダウンJLPT N1approx.Common
  noun, suru verb, transitive verb, intransitive verbA loanword noun that frames a decrease as a drop, something going down, rather than a neutral reduction. It fits a price or a number coming down, but is not the general word for decrease.
• 減らすへらすJLPT N3approx.Common
  godan verb, transitive verbThe transitive verb: to decrease, diminish, or abate something, or to shorten it. Use it when an amount, a number, or a cost is reduced by someone or something, rather than decreasing on its own.
  ジョギングでもして体重たいじゅうを減へらすようにしなさい。↗

  Try to lose weight by jogging.
• 低減ていげんCommon
  noun, suru verb, transitive verb, intransitive verbA noun for reduction or lowering, close to 減少; its senses include depreciation, and it is typical of technical and business writing rather than plain statements that something has decreased.
  産婦人科医さんふじんかいが減へっているのは出生数しゅっしょうすうの減少げんしょうで医療いりょうニーズが低減ていげんしたのを反映はんえいしている。↗

  The reduction in obstetricians and gynecologists is a reflection of the decrease in births, thus reducing need for medical care.

Use the verb 「減る」 when something decreases in size or number and 「減らす」 when something is decreased; among the nouns, 減少 is the neutral choice, 「ダウン」 frames a drop, and 低減 suits technical writing.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 減るへるto decrease (in size or number)
• 減少げんしょうdecrease
• ダウンfall
• 減らすへらすto abate
• 低減ていげんdecrease
• 減りへりdecrease
• 減収げんしゅうfall
• 減退げんたいdecline
• 減げんreduction
• 減ずるげんずるto decrease
• 減損げんそんdecrease
• 減じるげんじるto decrease
• 減却げんきゃくreduction
• 少なくなるすくなくなるto lessen
• 落ちるおちるto decrease (of popularity, quality, speed, sales, etc.)
• 目減りめべりdecrease (in value)
• 削げるそげるto weaken (e.g. of motivation, interest, etc.)
• 切るきるto reduce
• 緩むゆるむto decrease (e.g. speed)