half an hour or hour中文

half an hour or hour中文 half an hour or a half hour? 是half hour还是half an hour? a half hour还是half an hour? half hour =half an hour half an hour later half an hour? an hour and half还是an hour and a half The trains run every half an hour的中文 About half an hour ago.中文意思是? Half an hour =什么? half an hour? 什么意思?