The reconstruction of proto-forms is an attempt to determine what a language must have been like before any written records. However, even when we have written records from an older period of a language such as English, they may not bear any resemblance to the written form of the language found in today’s newspapers. some of the letters seem quite alien. The older letters þ (called “thorn”) and ð (“eth”) were both replaced by “th” (as in þu → thou, eorðan → earth), and æ (“ash”) simply became “a” (as in to dæg → today). To see how one language has undergone substantial changes through time, we can take a brief look at the history of English, which is traditionally divided into four periods.