Natlang

Proto-Indo-European was a natlang that can only be reconstructed with the help of its attested daughter languages.

Source: wiktionary

Regionalism is not a characteristic feature of natlangs, at least not in modern societies. People move around so much nowadays, that the effort is to conserve the differences rather than to conserve the similarities between different people's speech.

Source: wiktionary

is it true or not true that anything that can be said in mathematical notation, however advanced it may be, must at some point or another ALSO be sayable in ordinary natlang words?

Source: wiktionary

Don't expect me to waste my time learning a con-auxlang full of irregularities which I can already more or less understand and which won't gain me any access to other areas outside my own Romance area. I'll much rather use that time in learning the irregularities of a real natlang like, say, Arabic or Hindi, which will gain me access to the Arab and Indian areas, something which Interlingua won't do.

Source: wiktionary