順順地流下去（本義）
這一家族就是核心畫面本身：講一段話或一篇文章有沒有卡。
smooth speech or writing · adjective · B2
Fluent speech or writing runs on smoothly and confidently, with no long pauses, awkward parts, or mistakes, so it is easy to follow.
流暢的（言談或文字）
核心畫面
Water running in a stream — it keeps going without stopping, without catching on anything. One part flows straight into the next, and you never see it hesitate.
一條順順流著的水。它不卡、不停、不回頭，前一段直接接進後一段，中間看不到猶豫。這個字的重點從來不是「好」或「厲害」，…更多收起
一條順順流著的水。它不卡、不停、不回頭，前一段直接接進後一段，中間看不到猶豫。這個字的重點從來不是「好」或「厲害」，而是「不中斷」——東西一路過去，沒有卡住的地方。不管講的是語言、文字還是動作，卡住了就不叫 fluent。From the word’s history
Latin fluere 'to flow' — the same root behind fluid and influence. The word is literally about flowing.
來自拉丁文 fluere「流動」，跟 fluid（液體、流動的）、influence（本義是「流入」）同源。所以 fluent 從頭到尾就是「會流的」——把它想成水，比把它想成「語言程度」更接近這個字的原意。
Online Etymology Dictionary (etymonline.com), entry for 'fluent'
Two branches
外語說得順（最常見）
把「不卡」用到說外語上。學語言的人最明顯的卡點就是找字：想講一個東西，腦中先浮出母語，再翻，再說。fluent 的意思就是這個中間步驟消失了，話直接流出來。所以它形容的是順暢度，不是正確度——這也是為什麼一個人可以說得很 fluent 卻仍然有口音或小錯誤。
speaks a language well · adjective · B1
Able to speak and understand a foreign language very well, so that you can talk easily and quickly without stopping to search for words.
流利的；某語言說得很好的
原始詞典資料4 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。
fluencynoun/ˈfluːənsi/
- 1
The quality of smoothness of flow.
- She has fluency, nobility, / Elegance and symmetry, / Stability, fluidity, / Like poetry in motion.
- 2
human-scienceslinguisticssciencesThe quality of being fluent in a language; a person's command of a particular language.
- 3
The quality of consistently applying skill correctly in the manner of one well-practiced at it, requiring little deliberate thought to perform without mistakes
- While Gunners boss Arsene Wenger had warned his players against letting the pre-match festivities distract them from the task at hand, they clearly struggled for fluency early on.
- 4
The inherent ability to use a language easily and accurately.
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。