"a uniform" or "an uniform"?

"a uniform" or "an uniform"? a uniform还是an uniform a还是an uniform uniform前+a还是an 在英语里,是a uniform,还是an uniform wear a uniform为什么不用an wear a uniform 还是wear uniform 请问 a uniform gravitational field 中的 uniform 是He'got a uniform.还是He's got an uniform? _____ an ambulance man ______(wear) a uniform? "uniform"的前面是加"a",还是加"an"? I have uniform in my roomd在uniform前填什么冠词A an B a c some