“to register for a flight at the airport”
在機場辦理航班登記 “to register your arrival at a hotel”
（到達飯店時辦理入住） “to contact someone by making a phone call, short visit, etc., usually in order to make sure there are no problems or to tell them that there are no problems”
（透過電話、拜訪等確認沒有任何問題、或是向對方傳達沒有任何問題需要擔心）
（英文引用自劍橋字典）
因為①和②很常用、也很常聽到，所以應該有很多人都知道吧。
而③是確認「某人沒事吧」或「事情的進展沒有問題吧」等情況時使用的。
用到「check in」的例句
實際來看看有用到「check in」的句子吧。
I’m going to check in at Grand Prince Hotel at 5 pm today.
我預計今天下午5點要在格蘭王子飯店辦理入住。 We checked in at Suginoi Hotel at 10 pm today.
我們今晚10點在杉乃井飯店辦理了入住。 We were going to check in tomorrow afternoon but we canceled it.
我們本來明天下午要入住的，但我們取消了。 We went to the beach after checking in to Hoshinoya Hotel.
在星之屋飯店辦理入住後，我們去了海邊。
We checked in at the hotel before attending our friend’s wedding.
在參加朋友的婚禮之前，我們在飯店辦理了入住。 I have to check in by 7 pm.
我必須要在晚上7點之前辦理入住。 Can I check in now?
我可以現在辦入住手續嗎？ The guests who are going to check in at 9 pm tonight haven’t arrived yet.
預定今晚9點要入住的客人還沒抵達。 We have already checked in at the airport.
我們已經在機場辦好登機了。 He seemed so sleepy, so I constantly checked in.
他看起來很想睡，所以我頻繁的確認他的狀況。 I haven’t seen her for a while. I think we should check in every now and then.
我很久沒見到她了。我覺得我們應該要經常關心她 She caught a cold, so I check in every day.
她感冒了，所以我常常關心她的狀況。
You need to check out by 9:30 am.
你必須在9點30之前辦理退房。 We just checked out.
我們剛辦理退房。 We need to check out by 10 am the day after tomorrow.
我們必須在後天的早上10點之前辦理退房。 I’d like to check out.
我想要辦理退房。
②確認看看
My new song came out last week, so please check it out.
我上周剛發行新歌，請聽看看吧。 Thanks for sending the URL. I will check it out later.
謝謝你傳給我URL。我等等會確認的。 He has created a lot of works. You should check them out on his website.
他做出了很多的作品。你應該要去看看他的網站。 I want you to check it out from the link below.
我希望你可以確認一下下面的連結。
“to look at someone or something in order to make sure that they are safe, correct, etc”
為了確認安全、正確性等，檢查某人或某事物
（英文引用自劍橋字典）
也就是說，在檢查車子、飛機等有無異常，確認工作上沒有任何閃失、或確認事情的進展時可以使用它。
來實際看看幾個用到「check on」的句子吧。
I checked on his car.
我檢查了他的車子。 I checked on the cake in the oven.
我確認了在烤箱中蛋糕的狀況。
She checked on the progress of the project over and over again.
她多次地確認了關於那個項目的進展情況。 The staff are checking on the plane now.
工作人員們正在檢查飛機。 Could you please check on it for me?
可以請你幫我查一下那個嗎？ We should check on what’s happening here now.
我們應該要去確認一下這裡發生什麼事了。
有什麼感想呢？如果了解到它和「check in」用法上有什麼差別的話就太好了。
像這樣只有介係詞從「in」變成「on」意思就變得不一樣，這也是英文有趣的地方之一對吧！
「check in on」是什麼意思？
和「check in」很類似的表現，還有「check in on」。
像這樣連續使用「in」和「on」的詞語不多，因此對一些人來說這可能比較陌生。
「check in on」是「調查某事〜」的意思。用「check in on ＋人」可以表示「確認〜的狀況」「觀察〜的情況」。
它和之前介紹過的「check on」可能有點像，但「check in on」中「在事情發生了一段時間後，確認它目前的狀況。」這樣的意思比較強烈一點。
用「The Free Dictionary」查詢之後，出現了下面的說明。
“To actively monitor the security or safety of a person or thing.”
積極地監視某人或事物來確認其安全無虞
My mother checked in on me some days after the surgery.
在手術後的幾天，我媽來探望我了。 The nurse checked in on me every couple of hours.
護理師每過幾個小時都會來確認我的情況。 I went to the hospital to check in on my grandmother.
我去醫院探望了我的奶奶。 I checked in on my children playing in the living room.
我去確認了在客廳玩耍的孩子們的情況。 I try not to frequently check in on my subordinates.
