Translation guide
The English verb "soften" covers making something physically softer, reducing harshness of light/sound/color, and making attitudes, statements, or impacts gentler. Japanese uses different verbs depending on what is being softened.
To make a material, food, or substance less hard or firm.
General phrase for making something soft. Use for food, materials, etc.
バターを室温で柔らかくする。
Soften the butter at room temperature.
Formal/technical term for softening, often used in scientific or industrial contexts.
熱処理で金属を軟化させる。
Soften metal through heat treatment.
To soften by soaking in liquid, e.g., dried foods.
干し椎茸を水でふやかす。
Soften dried shiitake mushrooms in water.
To reduce intensity or harshness of sensory stimuli.
To soften, moderate, or ease. Works for light, sound, color, pain, etc.
照明を和らげる。
Soften the lighting.
声の調子を和らげる。
Soften one's tone of voice.
Also used for light, color, or texture, but 和らげる is more common for abstract softening.
色を柔らかくする。
Soften the color.
To reduce harshness, bluntness, or severity in communication or effect.
Most common for softening words, tone, criticism, or impact.
To ease, mitigate, or soften. Often used for regulations, conditions, or tensions.
規制を緩和する。
Soften regulations.
Loanword 'mild' used for softening taste, personality, or impact. Casual.
言い方をマイルドにする。
Soften the way of saying it.
To become soft or gentler on its own.
Intransitive form for physical softening.
バターが室温で柔らかくなった。
The butter softened at room temperature.
Intransitive for abstract softening: pain, anger, wind, etc.
痛みが和らいだ。
The pain softened.
和らげる is for abstract softening (light, sound, emotion, impact). 柔らかくする is for physical softening (texture, food). Overlap exists for color/light, but 和らげる is more natural for reducing harshness.
The loanword ソフト (soft) is mainly for software or texture. ソフトにする is not natural for softening light, sound, or attitude. Use 和らげる or 柔らかくする instead.