In the 20th cent. the structural or descriptive linguistics school emerged. It dealt with languages at particular points in time (synchronic) rather than throughout their historical development (diachronic). The father of modern structural linguistics was Ferdinand de Saussure, who believed in language as a systematic structure serving as a link between thought and sound; he thought of language sounds as a series of linguistic signs that are purely arbitrary, as can be seen in the linguistic signs or words for horse: German Pferd, Turkish at, French cheval, and Russian loshad'. In America, a structural approach was continued through the efforts of Franz Boas and Edward Sapir, who worked primarily with Native American languages, and Leonard Bloomfield, whose methodology required that nonlinguistic criteria must not enter a structural description. Rigorous procedures for determining language structure were developed by Kenneth Pike, Bernard Bloch, Charles Hockett, and others.
See also structuralism.