Joke exchanges are carried on in deadly earnest, like a verbal duel-mouth-to-mouth combat. Bang, bang: you’re (linguistically) dead. - David Crystal

There are the many daily examples of taboo speech, usually profanities or obscenities, that express such emotions as hatred, antagonism, frustration, and surprise. The most common utterances consist of single words or short phrases (though lengthy sequences may occur in 'accomplished' swearers), conveying different levels of intensity and attracting different degrees of social sanction.

For a language is really alive only as long as there is someone to speak it to. When you are the only one left, your knowledge of your language is like a repository, or archive, of your people’s spoken linguistic past. If the language has never been written down, or recorded on tape—and there are still many which have not—it is all there is. But, unlike the normal idea of an archive, which continues to exist long after the archivist is dead, the moment the last speaker of an unwritten or unrecorded language dies, the archive disappears for ever. When a language dies which has never been recorded in some way, it is as if it has never been.

The structural closeness of languages to each other has often been thought to be an important factor in FLL (foreign language learning). If the L2 [the foreign language] is structurally similar to the L1 [the original language], it is claimed, learning should be easier than in cases where the L2 is very different. However, it is not possible to correlate linguistic difference and learning difficulty in any straightforward way, and even the basic task of quantifying linguistic difference proves to be highly complex, because of the many variables involved.