a half hour还是half an hour?

a half hour还是half an hour?
a half hour还是half an hour?

a half hour还是half an hour?
它们的意思是一样的,美式英语里面多用half an hour,英式英语里面多用a half hour
半个小时的说法有：half an hour,a half hour,half of an hour（前两种用得多些）

意思一样都是半小时的意思

half an hour