Translation guide
The English verb 'redden' can mean to become red (intransitive) or to make something red (transitive). In Japanese, these are expressed with different verbs. The most common and natural way is to use 赤くなる (intransitive) or 赤くする (transitive). There are also specific verbs for blushing, ripening, or reddening due to inflammation.
To turn red or become red in color, often due to natural processes, emotions, or physical changes.
The most common and neutral way to say 'become red'. Used for leaves, sky, face, etc.
秋になると葉が赤くなる。
In autumn, the leaves turn red.
I was embarrassed and my face turned red.
Often used for cheeks, sky, or fruit becoming red. Slightly literary or poetic.
彼女の頬が赤らんだ。
Her cheeks reddened.
Specifically for skin flushing or blushing, often due to emotion or health. Formal/medical.
緊張で顔が紅潮した。
My face flushed with nervousness.
To cause something to become red, such as dyeing, painting, or applying color.
The most common way to say 'make something red'. Used for coloring, dyeing, etc.
彼は壁を赤くした。
He reddened the wall.
Often used for making one's cheeks red, e.g., with makeup or from emotion. Somewhat literary.
彼女は頬を赤らめた。
She reddened her cheeks.
Specifically when a person's face becomes red due to embarrassment, shame, or shyness.
The standard way to say 'blush' or 'one's face reddens'.
褒められて顔が赤くなった。
I blushed when I was praised.
A more formal or written term for blushing. Often used in literature or formal contexts.
彼は赤面して下を向いた。
He blushed and looked down.
When fruits or vegetables become red as they ripen.
Specifically for ripening and turning red. 熟す means 'to ripen'.
トマトが赤く熟した。
The tomatoes ripened and turned red.
General term for fruit/leaves changing color, not exclusively red. Often implies ripening or autumn colors.
リンゴが色づいてきた。
The apples are starting to redden.
When eyes or skin become red due to irritation, crying, or inflammation.
Specifically for eyes becoming bloodshot or skin becoming congested with blood.
泣いて目が充血した。
My eyes reddened from crying.
Can also be used for skin or eyes, but 充血する is more precise for bloodshot eyes.
アレルギーで肌が赤くなった。
My skin reddened due to allergies.
赤くなる is the most general and can be used for anything turning red. 赤らむ is often used for cheeks, sky, or fruit and has a slightly poetic nuance. 紅潮する is specifically for skin flushing and is more formal/medical.
There is no single Japanese verb that covers all uses of 'redden'. Always choose the expression based on whether it's intransitive or transitive, and what is becoming red.