1. 注意以下句型：

你把錢包放在這里真是太大意了。

正：It was careless of you to leave your wallet here.

正：You were careless to leave your wallet here.

以上第一句句首的 it 為形式主語，不能改為 that。但是若以上句型后面不出現不定式，那么句首的 it 也可換為 that。如：

他太粗心了。

正:It was very careless of him.

正:That’s very careless of him.

2. 比較：

正：He was careless to make the mistake. 他很粗心，結果出 了錯。(句中的不定式為結果狀語)

正：He was so careless as to make the mistake. (同上)

正：He was careless in typing the letter. 他打這封信時很 粗心。(句中的 in typing the letter有類似 when he was typing the letter 的意思)

誤：He was careless to type the letter. (若此句視為正句，則只能理解為：他很粗心，結果把那封信打印了出來)

3. 表示“不在意的”、“不關心的”等，其后可接介詞 about, of, with 等。如：

He’s careless of [about] his speech. 他講話隨便。

She is careless of [with] his health. 她不注意身體。

He is careless with his pronunciation. 他對語音不注意。

Don’t be so careless with your money. 你花錢不要這樣隨便。