The document summarizes the study of language change by providing examples from Old English to Modern English. It discusses [1] how sounds, words, and meanings have changed over time due to various linguistic processes, and [2] the main causes of language change including articulatory simplification, spelling pronunciation, analogy and reanalysis, language contact, assimilation, dissimilation, epenthesis, metathesis, weakening and deletion, auditory-based change, and phonological changes like splits and mergers. The high-level takeaway is that language is constantly evolving due to how it is learned and used by each new generation.