Yule's 5 features of human language
1. Displacement /Verdrängung = ability to talk about things, can also talk about hypothetical aspects, future events and not just about now
2. Arbitrariness/Willkürlichkeit = linguistic signs have no connection with what they present, no specific reason why we call a house, house
3. duality/Zweiteilung = words themselves are meaningless, become meaningful as they are combined (CAT zum Beispiel Bedeutung, während C, T, A unbedeutend sind)
4. Productivity (with help of rules new ways to combine, can create a new word, can change the meaning of an existing word, mail --> e-mail)
5. cultural transmission /Übermittlung (passed through social/cultural contact)