For 10 points, name this social science, which studies the nature of languages.
One important concept in this field is "diglossia," in which "Low" and "High" varieties exist simultaneously. Roman Jakobson and Nikolai Trubetzkoy belonged to the Prague School, which made important advances in this field. Ferdinand de Saussure wrote a general course in this field, whose important laws include Grimm's law. This field studies phonemes, units of sound, and morphemes, units of meaning. For 10 points, name this social science, which studies the nature of languages.
One important concept in this field is "diglossia," in which "Low" and "High" varieties exist simultaneously.
{linguistics}