Translation guide
The English word "erratic" describes something unpredictable, irregular, or inconsistent. This guide helps you choose the right Japanese expression depending on whether you mean unpredictable behavior, irregular movement, inconsistent performance, or a capricious person.
Describing something that does not follow a regular pattern, such as a person's actions, a vehicle's movement, or natural phenomena.
The most direct and common translation for 'erratic' when referring to irregular patterns, schedules, or movements. It is a neutral, widely understood term.
彼の睡眠パターンは不規則だ。
His sleep patterns are erratic.
バスの運行が不規則で困る。
The bus schedule is erratic and it's a problem.
Emphasizes instability or lack of steadiness. Often used for emotional states, weather, or mechanical performance.
彼の気分は不安定だ。
His mood is erratic.
この株価は不安定すぎる。
This stock price is too erratic.
Specifically for capricious or whimsical behavior, often of a person. Implies acting on a whim without consistency.
彼女は気まぐれで、約束をよく忘れる。
She's erratic and often forgets appointments.
Literally 'has unevenness', used for inconsistent performance or quality. Common in spoken Japanese.
彼の仕事にはむらがある。
His work is erratic (inconsistent).
Means random, haphazard, or nonsensical. Stronger than 'erratic', often implies lack of logic or order. Use with caution as it can sound negative.
Can sound harsh; not a direct equivalent for neutral 'erratic'.
彼の運転はでたらめだ。
His driving is erratic (reckless).
Describing something that varies in quality, such as work, sports, or machine output.
The most natural way to say performance is inconsistent or spotty.
彼のプレーにはむらがある。
His play is erratic.
Also used for unstable performance, especially in technical or formal contexts.
この機械の性能は不安定だ。
This machine's performance is erratic.
Describing physical movement that is unpredictable or jerky.
Works for any irregular movement.
ボールが不規則に跳ねた。
The ball bounced erratically.
Onomatopoeic adverb for unsteady, wobbling movement, like a drunk person or a poorly controlled vehicle.
Means meandering or zigzagging, specifically for a path. Often used for vehicles or rivers.
Describing a person whose behavior or decisions change unpredictably based on mood.
The standard term for a whimsical, capricious person. Can be used as a noun or na-adjective.
彼は気まぐれな性格だ。
He has an erratic personality.
Specifically for someone whose interests or affections change easily; fickle.
There is no single Japanese word that covers all nuances of 'erratic'. Using a dictionary lookup like 不規則 for every context can sound unnatural. Choose based on the specific meaning: irregularity, instability, inconsistency, or capriciousness.
不規則 (fukisoku) is for irregular patterns or schedules. 不安定 (fuantei) is for instability, often emotional or mechanical. 気まぐれ (kimagure) is for whimsical, mood-driven behavior. Use むらがある (mura ga aru) for inconsistent performance.
車がふらふら走っている。
The car is moving erratically.
The drunk driver was driving erratically (swerving).
彼女は移り気で、趣味がすぐ変わる。
She's erratic, her hobbies change quickly.