adj.粗心大意的，欠考虑的，轻率的

His thoughtlessness often leads to misunderstandings with his friends.
他常常粗心大意，导致与朋友产生误会。
She was annoyed by her roommate's constant thoughtlessness about cleaning up after themselves.
她对室友总是不收拾东西的漫不经心感到恼火。
The child's thoughtlessness regarding safety rules led to a near-miss accident.
孩子对安全规则的疏忽差点酿成事故。
His thoughtlessness towards her feelings was the reason their relationship ended.
他对她感情的忽视是他们分手的原因。
The boss appreciated the employee's thoughtfulness in preparing for the meeting.
老板赞赏员工为会议所做的周到准备。
Her thoughtlessness caused a significant delay in the project, which was highly inconvenient.
她的疏忽导致项目严重延期，给大家带来了不便。
His thoughtlessness towards the environment is reflected in his wasteful habits.
他对环境的漠视体现在他的浪费行为上。
It's important to be thoughtful when choosing gifts for someone, not just buy impulsively.
送礼物时要有心思，不能一时冲动。
The teacher scolded the students for their lack of thoughtfulness in class discussions.
老师责备学生们在课堂讨论中缺乏深思熟虑。
In life, it's crucial to practice thoughtfulness to avoid hurting others unintentionally.
生活中，我们一定要学会体贴入微，以免无意间伤害他人。