Explain why Searches allow the user to explore ups and downs in usage, how usages might change, acceleration or decline in usage, and how different sources use words or phrases differently. Carry out an empirical investigation of variation/change in English grammar/lexicon using corpus data. The specific topic of the paper is yours to decide. file 1: reference book file 2 and 3: samples (i have more samples) ***PS: The course is History of the English Language. The research should be about both history and corpus.