Translation guide
The suffix '-fold' is used in English to indicate multiplication or division, or to describe the number of parts or layers. In Japanese, there is no direct equivalent suffix; instead, you use specific counters, adverbs, or compound words depending on the context.
To express that something has increased or is multiplied by a certain number.
Attach the number to 倍 (bai) to mean 'X times'. This is the most common way to express multiplication.
利益が３倍になった。
Profits increased threefold.
人口は１０倍に増えた。
The population grew tenfold.
Use ～倍になる for intransitive 'become X times' and ～倍にする for transitive 'make X times'.
生産量を２倍にしてください。
Please double the production volume.
To express that something is divided or folded into a certain number of parts or layers.
Used for folding paper or cloth. The number is read with the native Japanese counter ～つ (e.g., 二つ折り = twofold, 三つ折り = threefold).
紙を三つ折りにしてください。
Please fold the paper in three.
二つ折りのパンフレット
a twofold brochure
Used for layers or thickness, e.g., 二重 (double-layered), 三重 (triple-layered).
Specifically for stacking flat objects like sheets or plates.
三枚重ねの毛布
a threefold blanket (three layers)
To describe something that consists of a certain number of elements, such as a 'twofold approach'.
Use the counter ～つ to list a number of aspects or parts. This is a flexible and natural way to express 'X-fold' in abstract contexts.
この計画には３つの目的がある。
This plan has a threefold purpose.
問題は２つある。
The problem is twofold.
Used for aspects or sides, e.g., 二面性 (twofold nature).
彼の性格には二面性がある。
His personality has a twofold nature.
Japanese does not have a single suffix like '-fold'. You must choose the appropriate counter or expression based on whether you mean multiplication, folding, layers, or aspects. Using 倍 for everything will sound unnatural.
倍 is for multiplication (increase, decrease, size), while つ折り is for physical folding. Do not confuse them: 'threefold increase' is ３倍, but 'fold in three' is 三つ折り.
価格が５倍になった。
The price increased fivefold.
手紙を三つ折りにしてください。
Fold the letter in three.
理由は２つある。
The reason is twofold.