to work or act together in order to bring about a result

aid, assist

to write one's name on the back of (a cheque)

support, authorize

to make (something) stronger by adding or supplying more people or material

strengthen, augment

to put (something) back in its place; to take the place of (a person, thing); to supply, use, (a person, thing) as a substitute

take the place of; put in place of

to take the place of (a person, machine, system etc)

displace, replace

to support or approve of (a person's behaviour, action etc); to confirm (a decision, a verdict) as correct

maintain, support