How to say "reinforcement" in Japanese

Choosing the right word
  • 強化きょうかJLPT N2approx.Common
    noun, suru verb, transitive verbThe general-purpose word: making something stronger, more intense, or more effective — rules, security, training, abilities. When you simply mean strengthening something, this is the word to reach for.
    我々われわれは組織そしきを強化きょうかしなくてはならん。↗
    We must beef up our organization.
  • 援軍えんぐんCommon
    nounReinforcements in the military sense: troops that come to the aid of a hard-pressed force. For 'send for reinforcements', this is the word you want.
  • 補強ほきょうJLPT N1approx.Common
    noun, suru verb, transitive verbReinforcement in a physical or structural sense: strengthening buildings, structures, or materials, or shoring up a weak point. Think of bracing something that might otherwise fail.
    コンクリートは中なかに鋼鉄こうてつの棒ぼうを入いれる事ことで補強ほきょうされる。↗
    Concrete can be reinforced by putting steel bars inside it.
  • 増強ぞうきょうJLPT N1approx.Common
    noun, suru verb, transitive verbAugmentation rather than repair: building up strength, capacity, or capability beyond its present level, as in expanding military power or organizational capacity.
    語彙力ごいりょくを増強ぞうきょうしたい。↗
    I want to build up my vocabulary.
  • 増援ぞうえんCommon
    noun, suru verb, transitive verbAlso military: additional troops sent to reinforce a unit or position. It stresses adding manpower, and overlaps with 援軍, which pictures the force arriving to help.
    これ以上いじょうここでもたついてると、後うしろの第だい二に関門かんもんからも増援ぞうえんが来きて、挟撃きょうげきされるかも知しれねーんだぜ。↗
    If we hang around here any longer, there could be reinforcements coming from the second gate to take us in a pincer movement!

Choose 強化 for strengthening or enhancement in general, 補強 for physically shoring up weak points, 増強 for building up strength or capacity, and 援軍 or 増援 for military reinforcements, with 援軍 stressing the force that comes to help.

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

Japanese equivalents
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JLPT vocabulary levels are community estimates, not official (no official lists have been published since the 2010 revision).

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