1 to use

2 to employ

3 to apply

4 to make use of

1 to use

2 to employ

3 to have to

4 to eat or drink

5 expense or outlay

6 usefulness

7 hence

8 therefore

1 user

2 consumer

3 subscriber

4 customer

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 need not

1 to do two things at once (idiom)

2 to multitask

3 to divide one's attention

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