Since the 1960s, computers have been able to store and analyze increasingly large amounts of data. Today, we can take all the words found in books, newspapers, magazines, and more, and store them in a database. What’s more, we can also do this with spoken language (although the process of converting it to text and storing it is more difficult).
Large collections of language, used for studying and analyzing the language, are called corpora. One collection is called a corpus. A good corpus which can give us reliable information about a language needs to be based on millions of words. The largest American corpus today consists of over 520 million words (http://corpus.byu.edu/coca/). In Britain, several exist containing over a billion words!
Most corpora of American (and British) English say the same thing: the most common word in English is the.
So it is not surprising: If we ask “What is the most common word in English?” we will see the word the in the question itself!!
What are some other very frequent words? And, be, of, to, a/an, in, have, that, I, are just some of the most common words which we are sure you already know!