HOW LANGUAGES CHANGE Languages continually undergo changes, although speakers of a language are usually unaware of the changes as they are occurring. For instance, American English has an ongoing change whereby the pronunciation difference between the words cot and caught is being lost. The changes become more dramatic after longer periods of time. Modern English readers may require notes to understand fully the writings of English playwright William Shakespeare, who wrote during the late 16th and early 17th centuries. The English of 14th-century poet Geoffrey Chaucer differs so greatly from the modern language that many readers prefer a translation into modern English. Learning to read the writings of Alfred the Great, the 9th-century Saxon king, is comparable to acquiring a reading knowledge of German.

A Sound Change Historical change can affect all components of language. Sound change is the area of language change that has received the most study. One of the major sound changes in the history of the English language is the so-called Great Vowel Shift. This shift, which occurred during the 15th and 16th centuries, affected the pronunciation of all English long vowels (vowels that have a comparatively long sound duration). In Middle English, spoken from 1100 to 1500, the word house was pronounced with the vowel sound of the modern English word boot, while boot was pronounced with the vowel sound of the modern English boat. The change that affected the pronunciation of house also affected the vowels of mouse, louse, and mouth. This illustrates an important principle of sound change: It tends to be regular—that is, a particular sound change in a language tends to occur in the same way in all words.

The principle of the regularity of sound change has been particularly important to linguists when comparing different languages for genetic relatedness. Linguists compare root words from the different languages to see if they are similar enough to have once been the same word in a common ancestor language. By establishing that the sound differences between similar root words are the result of regular sound changes that occurred in the languages, linguists can support the conclusion that the different languages descended from the same original language. For example, by comparing the Latin word pater with its English translation, father, linguists might claim that the two languages are genetically related because of certain similarities between the two words. Linguists could then hypothesize that the Latin p had changed to f in English, and that the two words descended from the same original word. They could search for other examples to strengthen this hypothesis, such as the Latin word piscis and its English translation, fish, and the Latin pes and the English translation, foot. The sound change that relates f in the Germanic languages to p in most other branches of Indo-European is a famous sound change called Grimm's Law, named for German grammarian Jacob Grimm (see Grimm Brothers).

B Morphological Change The morphology of a language can also change. An ongoing morphological change in English is the loss of the distinction between the nominative, or subject, form who and the accusative, or object, form whom. English speakers use both the who and whom forms for the object of a sentence, saying both “Who did you see?” and “Whom did you see?” However, English speakers use only the form who for a sentence's subject, as in “Who saw you?” Old English, the historical form of English spoken from about 700 to about 1100, had a much more complex morphology than modern English. The modern English word stone has only three additional forms: the genitive singular stone's, the plural stones, and the genitive plural stones'. All three of these additional forms have the same pronunciation. In Old English these forms were all different from one another: stan, stanes, stanas, and stana, respectively. In addition, there was a dative singular form stane and a dative plural form stanum, used, for instance, after certain prepositions, as in under stanum (under stones).

C Syntactic Change Change can also affect syntax. In modern English, the basic word order is subject-verb-object, as in the sentence “I know John.” The only other possible word order is object-subject-verb, as in “John I know (but Mary I don't).” Old English, by contrast, allowed all possible word order permutations, including subject-object-verb, as in Gif hie жnigne feld secan wolden, meaning “If they wished to seek any field,” or literally “If they any field to seek wished.” The loss of word-order freedom is one of the main syntactic changes that separates the modern English language from Old English.

D Semantic and Lexical Change The meanings of words can also change. In Middle English, the word nice usually had the meaning “foolish,” and sometimes “shy,” but never the modern meaning “pleasant.” Change in the meanings of words is known as semantic change and can be viewed as part of the more general phenomenon of lexical change, or change in a language's vocabulary. Words not only can change their meaning but also can become obsolete. For example, modern readers require a note to explain Shakespeare's word hent (take hold of), which is no longer in use. In addition, new words can be created, such as feedback.

E Change Due to Borrowing While much change takes place in a given language without outside interference, many changes can result from contact with other languages. Linguists use the terms borrowing and loan to refer to instances in which one language takes something from another language. The most obvious cases of borrowing are in vocabulary. English, for example, has borrowed a large part of its vocabulary from French and Latin. Most of these borrowed words are somewhat more scholarly, as in the word human (Latin humanus), because the commonly used words of any language are less likely to be lost or replaced. However, some of the words borrowed into English are common, such as the French word very, which replaced the native English word sore in such phrases as sore afraid, meaning “very frightened.” The borrowing of such common words reflects the close contact that existed between the English and the French in the period after the Norman Conquest of England in 1066.

Borrowing can affect not only vocabulary but also, in principle, all components of a language's grammar. The English suffix -er, which is added to verbs to form nouns, as in the formation of baker from bake, is ultimately a borrowing from the Latin suffix -arius. The suffix has been incorporated to such an extent, however, that it is used with indigenous words, such as bake, as well as with Latin words. Syntax also can be borrowed. For example, Amharic, a Semitic language of Ethiopia, has abandoned the usual Semitic word-order pattern, verb-subject-object, and replaced it with the word order subject-object-verb, borrowed from neighboring non-Semitic languages. Although in principle any component of language can be borrowed, some components are much more susceptible to borrowing than others. Cultural vocabulary is the most susceptible to borrowing, while morphology is the least susceptible.

F Reconstructing Languages Linguistic reconstruction is the recovery of the stages of a language that existed prior to those found in written documents. Using a number of languages that are genetically related, linguists try to reconstruct at least certain aspects of the languages' common ancestor, called the protolanguage. Linguists theorize that those features that are the same among the protolanguage's descendant languages, or those features that differ but can be traced to a common origin, can be considered features of the ancestor language. Nineteenth-century linguistic science made significant progress in reconstructing the Proto-Indo-European language. While many details of this reconstruction remain controversial, in general linguists have gained a good conception of Proto-Indo-European's phonology, morphology, and vocabulary. However, due to the range of syntactic variation among Proto-Indo-European's descendant languages, linguists have found syntactic reconstruction more problematic.