someday 只表示将来的 有一天
oneday 表示过去或将来的 有一天
someday
音标：英 ['sʌmdeɪ] 美 ['sʌmˌdeɪ]
释义：adv.将来有一天
例句：
1、I solemnly vowed that someday I would return to live in Europe
我郑重发誓，总有一天我将回到欧洲生活。
2、So you fancy yourself as the boss someday?
这么说，你是想有一天自己当上老板喽？
3、He took her left hand, hoping that it would someday bear a gold ring on the third finger.
他捧起她的左手，希望这只手的中指有朝一日会戴上一枚金戒指
oneday
音标： ['wʌndeɪ]
释义：n. 一天；（过去或将来的）某一天
例句：
1、Oneday, I took a rat home from the lab.
有一天，我从实验室带了一只老鼠回家。
2、Up to 5000 individual test results can be reported in oneday.
在一天之内，可以报告多达5000个单独的测试结果。
3、Oneday, after the coach informs him that he has not been called up for the nextchampionship fixture, the player leaves the club and does not appear fortraining on the following days.
有一天，当教练通知其没有被召入接下来参加赛事的阵容后，球员离开俱乐部，并在随后几天缺席训练。