A second language refers to a language that is different from the native or first language of a person. Additionally, this language is learned after the first language, and therefore can be learned even during adulthood. This causes in some cases the individual does not have the same pronunciation or proficiency of a native speaker.
Despite this, there is evidence and theories such as the critical period hypothesis that state this proficiency or pronunciation can be achieved if the individual learns the language early (approximately before adolescence) because before this stage children have more abilities to learn, they are not afraid of making mistakes and they can acquire, and remember language faster.
