i visited them once every six months的意思，还有另一种表达方式，用序数词~~

拜托，跪求啊！！

every second year是指每两年，这是常用表达法，由此推算每六个月应该为every sixth month
这个句子应该为i visited them once every sixth month，注意month不加复数的

i visited them twice a year

I visited them half a year.

你好！ I visited them twice a year.我一年看他们两次。 如有疑问，请追问。