New words：

detective [dɪˈtektɪv] n. 侦探；警探；私人侦探

Sample Sentences：

He buried himself in his detective story again.
Detectives have spent months gathering evidence.
A private detective had been tailing them for several weeks.

bury [ˈberi] v. 埋葬；埋藏

detect [dɪˈtekt] v. 发现；查明；侦察出

detection [dɪˈtekʃən] n. 探测；发现；侦查；察觉

New words：

thread [θred]
n.(棉、毛、丝等的)线；线索；思路；脉络
v.穿过；穿（针）

Sample Sentences：

Grandma sewed my trousers with thread.
The detective found a new thread in the case.
I'm afraid I've completely lost the thread of what you were saying.

The waiters threaded between the crowded tables.
It took me a long time to thread my way through the crowd.

detective [dɪˈtektɪv] n. 侦探；警探；私人侦探

New words：

calculation [ˌkælkjəˈleɪʃ(ə)n] n. 计算；预测；估计；算计

calculator [ˈkælkjəˌleɪtər] n. 计算器

Sample Sentences：

He made a mistake in his calculation.
Her calculation of the total was correct.
I can't work it out in my head ─ I need a calculator.

New words：

calculate [ˈkælkjuleɪt] v. 计算；预测；核算；推测

Sample Sentences：

She learned to calculate area in math class.
We calculate that we will arrive at 3 o’clock.
Can you calculate the sum of these numbers?

New words：

fasten [ˈfæs(ə)n] v.扣紧；盯住；盖好；使牢固

Sample Sentences：

The dog fastened its teeth in his leg.
She fastened the belt loosely around her waist.
She got quickly into her car and fastened the seat-belt.