Thoughtless describes someone who does not stop to think how their action will land on other people. They leave the last of the milk out on the counter, they play music loudly at midnight, they talk about a party in front of the one friend who was not invited.

Thoughtlessthoughtless describes someone用來形容一個人 who does not stop to think how their action will land on other people不會停下來想想自己的行為，會給別人帶來什麼影響。They leave the last of the milk out on the counter像是把最後一點牛奶放在流理台上沒收, they play music loudly at midnight半夜大聲放音樂, they talk about a party in front of the one friend who was not invited或是在唯一沒被邀請的朋友面前聊起某個派對。

The key thing — and it is the thing students most often miss — is that thoughtless is not the same as cruel. A thoughtless person is not trying to hurt you; that is exactly the point. Their mind was full of themselves and simply had no room for you in it.

The key thing重點 — and it is the thing students most often miss也是學生最常忽略的地方 — is that thoughtless is not the same as cruel在於thoughtless跟cruel（殘忍）不一樣。A thoughtless personthoughtless的人 is not trying to hurt you並不是想傷害你; that is exactly the point這正是重點所在。Their mind was full of themselves他們滿腦子只想著自己 and simply had no room for you in it根本沒有空間留給你。

That is why 'thoughtless' is a favourite word for gentle criticism between people who like each other: 'That was thoughtless of me, sorry.' Calling an act cruel ends a friendship; calling it thoughtless usually repairs one.

That is why 'thoughtless' is a favourite word for gentle criticism between people who like each other這就是為什麼在互相喜歡的人之間，「thoughtless」是個很常拿來溫和責備對方的字: 'That was thoughtless of me, sorry.'像是「That was thoughtless of me, sorry.」（那樣做我太不體貼了，抱歉） Calling an act cruel ends a friendship說一個行為cruel（殘忍）會讓友誼結束; calling it thoughtless usually repairs one但說它thoughtless通常反而能修補關係。

There is a second, more everyday use with no unkindness in it at all: done without thinking, careless. 'A thoughtless mistake' just means one made on autopilot. The context tells you which sense you are in — if there is a victim, it is the unkind sense.

There is a second, more everyday use with no unkindness in it at all還有第二種更日常、完全沒有惡意的用法: done without thinking, careless指沒經過大腦、隨便做的、粗心的。'A thoughtless mistake'「a thoughtless mistake」 just means one made on autopilot意思只是一個不經意犯下的錯。The context tells you which sense you are in前後文會告訴你是哪一種意思 — if there is a victim, it is the unkind sense如果有受害者，就是不體貼的那個意思。

Be careful with the shape of the word. It looks like the opposite of 'thoughtful', and in the being-kind sense it is. But 'thoughtful' has a second life meaning deep or reflective ('a thoughtful essay'), and 'thoughtless' does NOT reach into that meaning — the opposite of a thoughtful essay is a shallow one, never a thoughtless one.

Be careful with the shape of the word要小心這個字的長相。It looks like the opposite of 'thoughtful'它看起來像是「thoughtful」的反義詞, and in the being-kind sense it is在「體貼」這個意思上，確實是。But 'thoughtful' has a second life meaning deep or reflective但「thoughtful」還有第二個意思，是深刻、有省思的 ('a thoughtful essay')（像「a thoughtful essay」，一篇有深度的文章）, and 'thoughtless' does NOT reach into that meaning但「thoughtless」完全碰不到這個意思 — the opposite of a thoughtful essay is a shallow one, never a thoughtless one一篇thoughtful的文章，反義詞是shallow（膚淺），絕不是thoughtless。

Grammar note: it describes the person or the act, and the common frame is 'It was thoughtless of him to…'. Say 'thoughtless of', not 'thoughtless to' someone.

Grammar note文法小提醒: it describes the person or the act它可以形容人，也可以形容行為, and the common frame is 'It was thoughtless of him to…'常見的句型是「It was thoughtless of him to…」。Say 'thoughtless of'要說「thoughtless of」, not 'thoughtless to' someone而不是「thoughtless to」某人。