a group of countries, political parties, or people who have agreed to work together because of shared interests or aims

a military alliance 军事同盟

NATO is sometimes called the Atlantic Alliance. 北约有时被称作大西洋同盟。

an agreement to work with someone else to try to achieve the same thing

The three smaller parties have forged/formed an alliance against the government. 三个小政党结成反政府联盟。

Some of us feel that the union is in alliance with management against us. 我们中一些人感到工会和资方联合起来对付我们。