この製品は不良品だったので交換してもらった。
This product was defective, so I had it replaced.
彼は健康状態が不良で入院した。
He was hospitalized due to poor health.
noun, noun which may take the genitive case particle 'no', na-adjective
Refers to a person, especially a young person, who engages in antisocial or criminal behavior. Commonly used in 不良少年 (juvenile delinquent) or 不良グループ (gang of delinquents).
彼は昔、不良だったが今は真面目に働いている。
He used to be a delinquent, but now he works seriously.
夜の公園には不良がたむろしている。
Delinquents hang around the park at night.
Because his eyesight is poor, he wears glasses.
He was in a gang of delinquents back in junior high.
He couldn't advance to the next grade because of poor academic performance.
He turned into a delinquent in high school.
The match was cancelled due to bad weather.
不良 means a juvenile delinquent in general, while 番長 specifically denotes the leader or boss of such a group.
不良 is a broader, less slangy term for a delinquent teenager, while チンピラ specifically evokes a cocky, thuggish punk who may have gang ties.
不良 describes something as defective or poor in a more clinical, often technical sense, whereas 芳しくない is used more broadly for evaluations, results, or conditions.
不良 is a neutral, standard word for a juvenile delinquent, while ＤＱＮ is slangy internet shorthand with a strongly derogatory tone.
bad company; keeping bad company; getting mixed up with the wrong people
gang of hoodlums; bad company; delinquent friend