人身上的亮：這一刻的，與長期的
這一家就是核心畫面本身，亮的是人。兩個意思的差別只在時間長度：是此刻亮起來，還是本來就一直亮著。
cheerfulness (happy mood) · adjective · C2
The quality of feeling happy at this time, or of acting so other people can see you are happy.
愉快；開心
核心畫面
Picture a light that is on and shows outward. Cheerfulness is not just feeling good inside — it is brightness that other people can see and warm themselves at.
一盞亮著、而且照得到別人的燈。cheerfulness 不只是「心裡覺得快樂」，它一定要透出來——表情、聲音、動作，…更多收起
一盞亮著、而且照得到別人的燈。cheerfulness 不只是「心裡覺得快樂」，它一定要透出來——表情、聲音、動作，讓旁邊的人接收得到。這也是它和 happiness 最大的差別：happiness 可以完全藏在心裡，cheerfulness 幾乎一定是往外的。所以這個字後來能拿去形容房間、顏色、態度，因為那些東西也一樣在「往外散發亮」。From the word’s history
cheer originally meant the face or countenance (Old French chiere); to be of good cheer was to have a bright face. The outward, visible quality is in the word from the start.
cheer 這個字最早指的是「臉、面容」（古法文 chiere），be of good cheer 原意就是「臉色是好的」。所以「這份快樂是看得見的」不是後來才加上去的，而是這個字從一開始就長在臉上。cheerful 是 cheer + -ful，cheerfulness 再加 -ness，把那個亮著的表情變成一種可以談論的性質。
Wiktionary: cheerfulness < Middle English cherefulnes; cheer < Old French chiere "face, countenance" < Late Latin cara
Three branches
東西身上的亮：明亮宜人的空間與顏色
把那盞燈從人移到物。房間、顏色、擺設本身當然不會開心，但它們對人做的事和一個開朗的人一樣——你走進去就被照亮了，所以英文直接把同一個字借過去用。
cheerfulness (bright quality) · adjective · C2
The bright, pleasant quality of a place, a colour, or a thing that makes people feel happy when they see it.
明亮宜人
做事時的亮：欣然承擔
這一家把亮放進了「做事」的情境裡。前面幾層講的是狀態或感覺，這裡講的是態度——同一份亮，在有事要扛的時候會長成什麼樣子。
cheerfulness (willingness) · adjective · C2
A willing attitude that shows you will do whatever is needed, and that you do it happily, without complaining.
欣然；樂意
原始詞典資料1 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
cheerfulnessnoun/ˈt͡ʃɪɹfəlnəs/
- 1
The state of being cheerful; joy.
- Or he that exhorteth, on exhortation: he that giueth, let him doe it with simplicitie: hee that ruleth, with diligence: hee that sheweth mercy, with cheerefulnesse.
- The banded ones were all dressed in white gowns - a gay survival from Old Style days, when cheerfulness and May-time were synonyms - days before the habit of taking long views had reduced emotions to a monotonous average.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。