(c) Oxford English Dictionary (Reference in main text) From the website of the OED we can read that the “number of word forms defined and/or illustrated” is 615,100; and that we find 169,000 “italicized-bold phrases and combinations”. Therefore, we estimate an upper bound of the number of unique 1-grams defined by this dictionary as 615,100-169,000 which is approximately 446,000. III.4B. Estimation of Lexicon Size How frequent does a 1-gram have to be in order to be considered a word? We chose a minimum frequency threshold for ‘common’ 1-grams by attempting to identify the largest frequency decile that remains lower than the frequency of most dictionary words. We plotted a histogram showing the frequency of the 1-grams defined in AHD4, as measured in our year 2000 lexicon. We found that 90% of 1-gram headwords had a frequency greater than 10°, but only 70% were more frequent than 10°. Therefore, the frequency 10° is a reasonable threshold for inclusion in the lexicon. To estimate the number of words, we began by generating the list of common 1-grams with a higher chronological resolution, namely 11 different time points from 1900 until 2000 (1900, 1910, 1920, ... 2000) as described above. We next excluded all 1-grams with non-alphabetical characters in order to produce a list of common alphabetical forms for each time point. For three of the time points (1900, 1950, 2000), we took a random sample of 1000 alphabetical forms from the resulting set of alphabetical forms. These were classified by a native English speaker with no knowledge of the analyses being performed. The results of the classification are found in Appendix. We asked the speaker to classify the candidate words were classified into 8 categories: M if the word is a misspelling or a typo or seems like gibberish* N if the word derives primarily from a personal or a company name P for any other kind of proper nouns H if the word has lost its original hyphen F if the word is a foreign word not generally use