在口语中，可能everyday 和every day基本上也听不出来，不过考试可能会出这些没有什么意义的题呢。而且实际上它们也确实有点儿区别，还是以从有道词典上查的例句和解释为例吧。
every day 每一天
The enemy is there with their horses and camels, they are there every day.
everyday adj. 每天的，日常的
You use everyday to describe something that happens or is used every day, or forms a regular and basic part of your life, so it is not especially interesting or unusual.
如，As recently as 10 years ago, having one's picture taken was not an everyday occurrence.
日常英语，我们可以说 everyday English.
看到这里，个人觉得“我每天学英语”应该是 I study English every day.
不过 everyday 也有日常、平时的意思，如：
The girl helps her mother to wash up after dinner everyday.
She cooks and washes everyday.
这也是从有道词典上查到的例句。
好了，不说它了，下一话题，day in and day out。
day in and day out 也有天天的意思，但更强调的是夜以继日，即 without respite，all the time，与 day to day 一个意思。
如，Most people go through the same routine, day in and day out.
Daniel: Because you study day in and day out for the entrance exam. So I figure you would study even harder after you’ve got in.
耳边突然响起了电影《音乐之声》（The Sound of Music）里面可爱的童声“Can we do this every day?”
顺便学一下“隔天一次”怎么说，呵呵。
---Fraulein Maria, can we do this every day?
---Don't you think you'd soon get tired of it, Louisa?
---I suppose so. Every other day?
2016-08-10
