Contrast the slang that is used today with the 'periodic' english.
For e.g, instant messaging has brought about a new language. (Everything is abbreviated. There is no proper use of grammar.)
However, in ancient times english language was different. (In the Shakespearan era, for example - in the times of the greatest poets. Refer to the use of 'thou' 'thy' 'shalt' etc.)
*Please find technical terms for what I've mentioned. I'm only giving broad ideas.
