在華語教學這個領域，筆者常常碰見誤用second language與foreign language的例子。有一次在美國問別人：「你們說你們的產品是給CSL(Chinese as a second language)的學生使用，你們針對的對象是華裔嗎？」還被人家質疑我怎麼充內行。現在就來看看是怎麼定義的。
依Ellis(1994)的說法：
In the case of second language acquisition, the language plays an institutional and social role in the community (i.e., it functions as a recognized means of communication among members who speak some other language than their mother tongue). For example, English as a second language is learnt in the United States, the United Kingdoms, and contries in Africa such as Nigeria and Zambia (pp. 11-12).
嚴格地說，第二語言是該語言在當地有溝通作用的，是能在生活中使用的。像許多美國移民，他們有自己的母語，英語是後來才學的，但卻是生活中與他人溝通的語言。依此定義，Chinese as a second language在美國所包涵的範圍變小很多。除了課堂之外，能與他人練習多半是華裔子弟。
至於foreign language，Ellis(1994)的解釋是：
In contrast, foreign language learning takes place in setting where the language plays no major role in the community and is primarily learnt only in the classroom. Example of foreign language learning are English learnt in France or Japan (p. 12).
從Ellis的解釋可以清楚看出來，如果外國學生在台灣學習，在課堂外有許多使用的機會，這可算是第二語言學習。但如在美國學中文，如果父母沒有中文背景，那多半就是在課堂上學習，這應該稱作CFL(Chinese as a foreign language)。
雖然在台灣華語教學常翻成TCSL(teaching Chinese as a second language)，但嚴格說來這樣的翻譯有其侷限性。早期台師大華研所所名為Graduate Institute of Teaching Chinese as a second/foreign language，也不知何時foreign就悄然消失了。TCSL這幾年名號打響了，實無改變的必要。但在使用CSL或CFL時，不可不慎！
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