The document summarizes four methods of comparative study of languages:
1) The historical comparative method reconstructs ancestral languages by comparing resemblances in descendant languages to prove common descent. Developed through Indo-European studies, it is the standard for determining language relatedness.
2) The areal comparative method studies languages in geographic contact areas and looks at common features from language interaction rather than genetic descent.
3) The typological comparative method groups unrelated languages based on present-day linguistic characteristics without considering history.
4) Contrastive analysis systematically compares language pairs to identify structural differences and similarities, examining both related and unrelated languages.