1 to substitute for

2 to take the place of

3 to replace

4 for

5 on behalf of

6 to stand in for

1 to replace

2 alternately

3 in turn

1 to replace

2 to take the place of

1 to take over (from one another)

2 to alternate

3 to replace

4 to relay

1 to substitute for

2 to replace

3 to supersede

1 to assume sb's name and take his place (idiom); to impersonate

2 to pose under a false name

1 to do everything oneself (idiom); not to allow others in on the act

1 to fret over the worries of long-departed people (idiom); to worry unnecessarily

2 crying over spilt milk

3 often used with negatives, e.g. no need to worry about past issues

1 to fret over the worries of long-departed people (idiom); to worry unnecessarily

2 crying over spilt milk

3 often used with negatives, e.g. no need to worry about past issues