1 letter

2 mail

3 classifier: 封 fēng

4 to trust

5 to believe

6 to profess faith in

7 truthful

8 confidence

9 trust

10 at will

11 at random

1 information

2 news

3 message

1 to be convinced (that sth is true)

2 to believe

3 to accept sth as true

1 text message

2 SMS

1 by means of

2 through

3 via

4 to pass through

5 to get through

6 to adopt

7 to pass (a bill or inspection etc)

8 to switch over

1 proficiency in a particular field (idiom)

2 skill in a specialized area (idiom)

1 lit. doesn't (even) enter a single aperture (of one's head)

2 I don't understand a word (idiom)

3 it's all Greek to me

1 grasp this fundamental point and all the rest will follow (idiom)

1 to act in collusion (idiom)

1 mutual exchange of assistance (idiom)

2 to benefit from each other's strengths and make up each other's shortfalls

3 to reciprocate with material assistance

4 scratch each other's back