Merge and Alliance

Merge

When two things blend together to form one whole they merge, as with two companies that join to make one. We also say merge to describe how a car slowly or carefully enters traffic on the freeway or a busy street.
Arbor Drugs and CVS used to be competing pharmacies, but several years ago they merged. Now they're just one large company that is called CVS Drugs.
Sherry is a pretty good driver, but she is still not very good at merging. When she turns onto the highway or a busy street, other cars often have to slow down a bit to let her in.
When two companies join or merge into one it is called a merger. When someone or something leaves a group and comes out alone they emerge.
After the merger, our jobs changed a lot. The company got all new managers from our partners and they wanted to change all the basic policies.
After a long race that was very close, the Kenyan runner emerged as the winner. He began to run past the other contestants in the final minutes of the race.

Alliance

An alliance is a partnership, usually between two or more countries or organizations, for mutual interest.
The European Union is one of the largest alliances in the world. All its member states are joined together for mutual economic gain.
The Republican party today represents an uneasy alliance between Christian conservatives and free-market business interests. It's unclear which faction would win if they had a disagreement.
Countries or partners in an alliance are allies. Ally is the singular term.
In the Second World War, the United States' allies included Britain, France, and the Soviet Union. They are often called the Allied Powers for short.
City Hall and the Department of Social Services have really been our allies in the struggle to reform the unemployment insurance system. They've managed to pressure the state government to take action better than our tiny organization can.