"My birthday is on October 18th."
"October" 是十月的意思，来源于拉丁语 "octo" 意为 "八"，因为古罗马历法中十月是第八个月。
"18th" 是序数词形式，表示第十八个。
例句：
"My sister's birthday is on October 18th." (我姐姐的生日是十月十八日。)
"I'm planning a surprise party for my friend's October 18th birthday." (我正在为我朋友的十月十八日生日计划一个惊喜聚会。)