Wiktionary
n. 1 A language that is not widely or officially spoken in a particular place. 2 A language that is not one's native tongue.
Wikipedia
A foreign language is a language indigenous to another country. It is also a language not spoken in the native country of the person referred to, i.e., an English speaker living in Guam can say that Chamorro is a foreign language to him or her. These two characterisations do not exhaust the possible definitions, however, and the label is occasionally applied in ways that are variously misleading or factually inaccurate.
Some children learn more than one language from birth or from a very young age: they are bilingual or multilingual. These children can be said to have two, three or more mother tongues: neither language is foreign to that child, even if one language is a foreign language for the vast majority of people in the child's birth country. For example, a child learning English from his English father and Irish at school in Ireland can speak both English and Irish, but neither is a foreign language to him. This is common in countries such as India, South Africa, or Canada due to these countries having multiple official languages.
In general, it is believed that children have advantage to learning a foreign language over adults. However, there are studies which have shown adult students are better at foreign language learning than child students. It is because adults have pre-existing knowledge of how grammar works, and a superior ability of memorizing vocabulary.
Usage examples of "foreign language".
Its parent tongue, Anglo-Saxon, was more highly inflected than its descendant-less so than Latin, but about as much so as modern German* Anglo-Saxon would sound to a modern hearer as much like a foreign language as German.
He spoke a few quick words in a foreign language to the Chinese on his right, a tall sinewy intelligent looking man with a face as still as Hewell's own, then turned back to me.
The sharp clacks of a game of pool rose from the floor of the spur, punctuated by exclamations in a foreign language.
As the soldiers passed him, Park caught a sentence in a foreign language, sounding like Spanish.
She had stuck it through the endless tedium of countless diplomatic cocktail parties, although she spoke no foreign language, while her husband made the rounds, elegant, affable, fluent in English, French, and German, doing his job under embassy cover.
Spanish would constitute his third foreign language, but more, it would open up the whole Latin American Division to him.
She washed her hands in water and some sharp-smelling liquid that her attendants brought, examined the wound, then spoke in a sharp, nasal-sounding foreign language.