Regarding the speakers, one of the reasons is the colonization, which increases numbers of English speakers around the world. As English becomes an international language, many varieties, dialects, and accents are existing, so these different Englishes make big changes in the standard language. Linguistic freedom may lose the language identity, so dictionaries were commissioned to reinforces the need for unified and codified language, to protect the language. In addition, dictionaries help English speakers and learners to write correctly and elegantly, through setting spelling, orthographic, and structure systems. Noah Webster’s dictionary (1828) which produced after the American independence from Britain, basically formed to purify the language from errors, and to reform spelling in American English. Webster’s dictionary focused on the differences in spelling and pronunciation between American and British English, as color in American’s, colour in British. (Merriam-webster.com, 2017)In the past, the criteria used for including words in the dictionary differ from the recent days. Most dictionaries depended on personal invitations, and were codified a list of words that most writers thought that these words would be useful. For example; Shakespeare, the great writer and poet, invented over 1700 words like swagger and torture. However, modern dictionaries don’t allow personal invitations, their criteria depend on words used by various writers, not just one writer ‘as in Shakespeare period’, so these words become candidates to include them into dictionaries. Oxford University Press developed criteria for including words in the dictionary, they called it corpus which is a database contains ‘a collection of texts of written or spoken language presented in electronic form’ (Anon, 2017). Corpus help lexicographers to decide if new words will include in the dictionary or not. Corpus contains 2.5 million words of the 21st century, and editors update corpus every three months. This process mainly based on three stages: reading, recording, and confirmation.First; over fifty editors and lexicographers in the Oxford Corpus read printed novels, newspapers, books, magazines, TV transcripts, and websites to look for new words. Second, when they notice a new word like a word ‘tweet’ that has new a use for an existing word, editors record it in the database in the computer system. Third, editors create citations for each word, they include the new word, examples of the new word used in the context, and the source they found this new word from. In this stage they follow a rule of five that thought if a new word has been in print five times, in five different resources over a period of five years, then they confirm to add a new word in the dictionary. After these three steps, new words are included in the dictionary. There are two main types of dictionaries; prescriptive and descriptive dictionaries. Prescriptive dictionaries tend to believe that a language can be fixed (Seargeant and Swann, 2012), and codified through outlining the language rules, and explaining norms that should be followed or avoided in language usage. For example; prescriptive dictionaries clarify that we shouldn’t end the sentence with the proposition as in ‘Which student did you talk to?’. It is grammatically wrong despite using this rule in daily conversation, it should be ‘To which student did you talk?’. Johnson’s Dictionary and Noah Webster’s Dictionary considered as prescriptive dictionaries, they teach us how to use a language in a correct or proper way. Consequently, they aimed to promote standard English and keep the language in its original form. They tried to develop rules depending on Latin grammar and attempted to fixed spelling and meaning.On the other hand, descriptive dictionaries analyse and describe the language usage and behaviours, which reflect the actual language, not the standard one. The language rules emerge from how people use the language, so they work as documents. Therefore, common words, grammars, and spellings are included in descriptive dictionaries even they are non-standard (Englishplus.com, 2017). For example, many of native speakers use ‘ain’t’ when they are speaking, but in fact, using ‘ain’t’ is not grammatically correct. Likewise, linguistics in descriptive dictionaries believe that sentences that produced by native speakers like ‘Emma reads a book’ which are formed by adding -s to the third person are grammatically correct. Most of the modern English dictionaries are descriptive, for instance; Oxford English Dictionary.Both of two types of dictionaries are important. Descriptive dictionaries which are modern concepts, clarify how people speak, so they help non-speakers to learn the language. As for prescriptive dictionaries which are traditional concepts, concern about the correctness, thus they help native speakers who want to make sure about such a word meaning, spelling, or grammar rule.In conclusion, this paper analyses the codification which considered as a linguistic form of standardization, and the history of how language is codified in dictionaries through the 16th and the 18th centuries. It also mentioned the reasons of dictionaries commissioned regarding the language itself and to the speakers, and the criteria used for including words in the dictionary. Finally, it clarifies the extent to which a dictionary is considered to be a prescriptive or descriptive account of English.