根據英國著名的朗曼出版社出版的《朗曼應用語言學詞典》所給的定義是：
The use of a second or foreign language in school for the teaching of content subjects.
Bilingual education programs may be of different types and include:
a) the use of a single school language which is not the child’s home language. This is sometimes called an immersion program.
b) The use of the child’s home language when the child enters school but later a gradual change to the use of the school language for teaching some subjects and the home language for teaching others. This is sometimes called maintenance bilingual education.
c) The partial or total use of the child’s home language when the child enters school, and a later change to the use of the school language only. This is sometimes called transitional bilingual education. “雙語教學”項目可以有不同的形式，包括：
A) 學校使用壹種不是學生在家使用的語言進行教學。這種模式稱之為：浸入型雙語教學。
B) 學生剛進入學校時使用本族語，然後逐漸地使用第二語言進行部分學科的教學，其它學科仍使用母語教學。這種模式稱之為：保持型雙語教學。
C) 學生進入學校以後部分或全部使用母語.
簡言之，“雙語”和“雙語教學”的界定是：將學生的外語或第二語言，通過教學和環境，經過若幹階段的訓練，使之能代替，或接近母語的表達水平。例如：加拿大奎北克省，同時使用法語和英語，並以法語為其官方語言壹樣。更通俗地打個比喻，某個西藏同胞既可以在家裏用藏語和家人交流，也可以用漢語在工作單位與同事交流。