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.

New words：

steward [ˈstuərd] n.（飞机、轮船、火车等的）服务员；男服务员；乘务员
stewardess [ˈstuərdəs] n.（飞机、轮船、火车等的）女乘务员；女服务员

Sample Sentences：

The steward helped the old man find his seat.
The ship’s steward checked the passengers’ tickets.

The stewardess served meals during the flight.
The stewardess showed us how to fasten the seatbelt.

fasten [ˈfæs(ə)n] v.扣紧；盯住；盖好；使牢固