Medgyes (1992) defines a native English speaker as a person who was born in English speaking countries and can use the English language fluently and accurately with native-like competence as a first language. With regard to the definition of a non-native English speaker, Liu (1999) defines a non-native English speaker as a person who was born in non-English speaking countries and who can use the English language as a second or foreign language with non-native-like proficiency and competence.
Crystal (1995: 455) defines a native speaker simply as "A person who speaks a language as a mother tongue". He / she, therefore, is somebody born into a particular language, using this language as an instrument of communication and as a symbol of social identification at the same time. A non-native speaker however is a person who does not have that language as a mother tongue. This leads to put the non-native speaker in the position of having that language besides his/her own mother tongue and acquiring it for some reason at some point in their lives.