After 可當介系詞、連接詞和副詞用，而 afterwards 只能當副詞用。
After 用作介系詞時意為「(時間、地點或順序) 在 … 之後，在 … 以後；在 … 後面；隨 … 之後」。例如：
- They’re planning to meet at half after seven. (他們打算七點半見面)
- Let’s go for a walk after dinner. (我們晚餐後去散步吧)
- Mary came in after John. (瑪麗在約翰之後進來)
- There’s a good concert on the day after tomorrow. (後天有一場不錯的音樂會)
- His house is just after the park, on the right. (他的房子就位在公園的後面，在右邊)
- My name came after his on the list. (名單上我的名字排在他後面)
After 用作連接詞來引導副詞子句時意為「在 … 之後，在 … 以後」。若該副詞子句是指未來時間，則該子句只能使用現在簡單式來表示未來，不能有 be going to、shall 或 will 等表示未來的字眼。例如：
- I went to the library straight/immediately after I left the dormitory. (我離開宿舍後就馬上/立刻上圖書館)
- Soon/shortly after I left, I realized I had forgotten to switch the TV off. (我離開不久後就意識到忘了關電視)
- We’ll contact you after we arrive in Bangkok. (我們抵達曼谷後會跟你聯絡) (正)
We’ll contact you after we are going to arrive in Bangkok. (誤) - Hilary will move to Kaohsiung after she gets married. (希拉蕊結婚後將搬到高雄) (正)
Hilary will move to Kaohsiung after she will get married. (誤)
After 亦可當副詞用，意為「之後，以後，後來」，但 afterwards 比較常見。當 after 被用作副詞時，它通常是某副詞片語的一部份。另外，值得一提的是，afterwards 是美式英語和英式英語通用的副詞，而美式英語還可使用 afterward。例如：
- Nina and Roger lived happily ever after. (妮娜和羅傑從此過著幸福快樂的生活)
- Judy got here in the afternoon and Wilson arrived soon after. (茱蒂下午到了這裡，隨後不久威爾森也到了)
- I can’t go to see Vivian next week – how about the week after (= the following week)? (下個禮拜我不能去探望薇薇安，下下個禮拜怎麼樣？)
- They got divorced and soon/shortly afterwards Melody moved to the country. (他們離婚後不久美樂蒂就搬到了鄉下)
- If I’m a good boy at the doctor’s, will you take me swimming afterwards? (如果我在診所時很乖，之後你會帶我去游泳嗎？)
- Let’s go and see a movie and afterward we could go for a meal. (我們去看場電影，之後可以去吃頓飯)