"My birthday is on October 3rd" 或 "My birthday is October 3rd" 是表达生日在10月3日的正确英语表达方式。
其中 "October" 是英语中表示10月的词汇，来源于拉丁语"octo"，意为"八"，因为古罗马历法中10月是第八个月。而 "3rd" 则表示第三天。
例句：
"My birthday is on October 3rd, so don't forget to buy me a present!" (我的生日是10月3日，所以别忘了给我买礼物！)
"I can't wait for my birthday on October 3rd, it's going to be a great day!" (我等不及我10月3日的生日了，那一天一定会很棒！)