1 to be connected

2 traffic

3 transportation

4 communications

5 liaison

1 common

2 ordinary

3 general

4 average

1 to join

2 to connect

3 to link up

4 to communicate

1 interaction

2 social contact

1 community

2 neighborhood

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

1 lit. the Eight Immortals cross the sea, each showing his own special talent (idiom)

2 fig. (of each individual in a group) to give full play to one's unique capabilities