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 mutual

1 to compete with (idiom) (Tw)

2 to pit oneself against

1 mutually related karma (idiom); fates are intertwined

2 interdependent

1 mutually shirking responsibilities (idiom); each blaming the other

2 passing the buck to and fro

3 each trying to unload responsibilities onto the other

1 to confide in each other (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