The influence of French on the English language pertains mainly to its lexicon, but also to its syntax, grammar, orthography and pronunciation. The majority of the French vocabulary in English entered the language after the Norman conquest of England in 1066, when Old French, and specifically the Old Norman dialect, became the language of the new Anglo-Norman court, the government, and of the elites for several centuries. This period lasted until the aftermath of the Hundred Years' War (1337–1453). Even since then, English has continuously been influenced by the French language.
According to Laura K. Lawless, more than a third of the modern English lexicon is of French origin, while Henriette Walter claims that the total is as high as two thirds. Anthony Lacoudre has estimated that over 40,000 English words come directly from French and may be understood without orthographical change by French speakers.
At the beginning of the 11th century, Old English was not a single unified language, but a dialect continuum that stretched from the southern English coast to the Forth estuary. However, a literary standard had emerged, based around the West Saxon dialect spoken in the area centered around Winchester, the capital of Wessex. Also spoken in the territory ruled by the Anglo-Saxons were the Celtic languages of Old Cornish, Old Welsh and Cumbric, mainly in peripheral regions where settlement by the Anglo-Saxons had been fairly minor, and Old Norse, across a wide swathe of territory in the north and east midlands.
William II of Normandy landed at Hastings (in Sussex) on September 29, 1066. He deployed his men in the nearby area while waiting for King Harold Godwinson's troops. On October 14, exhausted by previous clashes with Scandinavians in the north and the long journey to Hastings, the English army lost the battle quickly, becoming disorganized after Harold himself was killed. Following the defeat of the English, William claimed the throne as King of England on December 25, 1066; he was crowned William I of England and came to be known as William the Conqueror (Guillaume le Conquérant in French). William's followers became a new Norman ruling class, and imposed their language into the upper echelons of society; Anglo-Saxon dialects were supplanted by Norman in the royal court and aristocratic circles, the justice system, and the church. Influential Norman settlers continued to use their native language in daily life, while more modest, rural, and urban areas of society continued to speak varieties of English.
The Norman conquest marked the beginning of a long period of interaction between England and France. Noble English families, most of them of Norman origin, taught their children French or sent them to study in France. The early Norman kings spent more time in Normandy than they did in England. Royal marriages also encouraged the expansion of the French language in England. From Henry II Plantagenet and Eleanor of Aquitaine at the beginning of the 12th century, to Henry VI and Margaret of Anjou in the 15th century, many English kings married French princesses. These marriages kept French as the language of the English court for several centuries and strengthened its use in England overall.
Throughout the late 11th and 12th centuries, the Norman nobility had ruled over both England and Normandy. However, in 1204, Normandy was lost to France, and as a result the aristocracy began to associate more with an English identity. Anti-French sentiment in England began to grow when Henry III invited relatives of his wife Eleanor of Provence to settle in England, bestowing lavish favours on them. Written works promoting the use of English in England began to appear at around this time, such as the Cursor Mundi. Meanwhile, the French spoken in England was stigmatised as a provincial variety by speakers from the continent, particularly because the Anglo-Norman language that was spoken by the elites had taken on a syntactical structure that resembled English. Some nobles had simply shifted to English entirely.
In 1328, Charles IV of France died without an heir. Edward III of England and Philip VI of France disputed the French throne, and the Hundred Years' War ensued. The war provoked further negative feelings towards French in England, as it came to be seen as the language of the enemy. By now, English was re-asserting itself as a language of government and learning after over 200 years as a low-status language. In 1349, English became the language of instruction at the University of Oxford, which until then had taught in French or Latin. The use of English became widespread thanks to the introduction of printing to England by William Caxton in 1476. Henry IV (1367-1413) was the first English king to have English as his first language, and Henry V (1387-1422) was the first king of England to use English in official documents.
The 16th century, that of the Renaissance, was a decisive century for the French language since King François I of France, through the Ordonnance de Villers-Cotterêts (1539), made French the official language of administration in the whole kingdom; the Duchy of Savoy had established French as its administrative language a few decades earlier. Although troubled by the European wars of religion and the Italian Wars, the language was marked by intellectual, technical and scientific effervescence.
The 17th century, the apogee of France's Old Regime, was characterized by the political, literary and artistic prestige of France and the French language. Peace restored and unity ensured in the country, the economy grew considerably. King Henri IV, the Cardinal of Richelieu and Louis XIV, The Sun King helped seed and enhance the French language in Europe, the Americas, India and Oceania.
The creation of Académie française by Richelieu in 1635, under Louis XIII, led to the standardisation of French in continental Europe and abroad, including England. French was then the second language of all the elites in Europe, from Turkey to Ireland and Moscow to Lisbon. The greatest scholars and intellectuals, writers and scientists, expressed themselves and corresponded in this new standardized French. French was considered a perfect language, of beauty and elegance determined by scientific logic, aided by dictionaries (the first encyclopedia was published by Diderot and other French scientists, 1751-1772). Scholars and intellectuals, writers and scientists, expressed themselves and taught in French.
The Age of Enlightenment, which began with the death of Louis XIV in 1715 and ended with the French Revolution of 1789, was the start of a new era for France. Important reforms were introduced, such as the abolition of torture or the Edict of Tolerance towards Protestants. It was also the century of scientific interests and the development of encyclopaedias.
The most notable influence of French on English has been its massive contribution to the English lexicon. It has been estimated that about a third of the words in English are French in origin; linguist Henriette Walter claims that this total may be as high as two thirds. Anthony Lacoudre has estimated that over 40,000 English words come directly from French and may be understood without orthographical change by French speakers.
Albert C. Baugh and Thomas Cable note that "although this influx of French words was brought about by the victory of the Conqueror and by the political and social consequences of that victory, it was neither sudden nor immediately apparent. Rather it began slowly and continued with varying tempo for a long time. Indeed, it can hardly be said to have ever stopped." Baugh and Cable define several categories of early French borrowings:
In many cases a French word might have existed alongside a Germanic word that meant the same thing, with the two words eventually taking on different senses. Exemplifying this are the "food pairs" in which the English word refers to a living animal on a farm, while the French word signifies the meat of the animal after it has been made into a meal (cow and beef, swine and pork, sheep and mutton). Other times, the same French word was borrowed twice, once from the Norman dialect and then again from the Parisian dialect, with different meanings arising. Such doublets include Norman catch vs Parisian chase, Norman warranty vs Parisian guarantee and Norman warden vs Parisian guardian.
The period from 1250 to 1400 was the most prolific for borrowed words from French. Forty percent of all the French words in English appear for the first time between these two dates. After this period, the scale of the lexical borrowing decreased sharply, though French loan words have continued to enter English even into the modern era.
The gradual decline of the English singular pronouns thou and thee and their replacement with ye and, later, you has been linked to the parallel French use of vous in formal settings. The ubiquity of -s to mark plurals in English has also been attributed to French influence; however, the -s ending was common in English even prior to the Norman Conquest, since -as was the standard suffix form for plurals of strong masculine nouns in the nominative and accusative cases. It is possible that the dominance of this form over other endings such as -en was strengthened by the similarity of the French plural construction. 
Other suggestions include the impersonal one (i.e. "one does what one wants") and possessive phrases such as "the guitar of David" rather than "David's guitar." Forms similar to these are found in other Germanic languages, though, casting doubt on the proposed French derivations. Attempts have also been made to connect the increased use of gerunds towards the end of the Middle English period to the French gérondif form.
While fairly rare in English, constructions that place the adjective after the noun (i.e. attorney general) are derived from French.
English has adopted several prefix and suffix morphemes from French, including pre-, -ous, -ity, -tion, -ture, -ment, -ive, and -able. These now stand alongside native English forms such as over-, -ish, -ly, -ness, -ship, -some, -less, and -ful.
The influence of French on English pronunciation is generally held to have been fairly minor; however, a few examples have been cited:
In the centuries following the Norman conquest, English was written mainly by Norman scribes. Thus, French spelling conventions had a great effect on the developing English orthography. Innovations that arose during this period include:
Several letters derived from Germanic runes or Irish script that had been common in Old English, such as ƿ and ð, largely fell out of use during this period, possibly due to the Normans' unfamiliarity with them. þ, the final remaining runic letter in English, survived in a severely altered form until the seventeenth century.
The effects of the Norman conquest had indirect influences on the development of the standardized English which began to emerge towards the end of the fifteenth century. The takeover of the elite class by the Normans, as well as their decision to move the capital of England from Winchester to London, ended the dominance of the Late West Saxon literary language. London's growing influence led to the English spoken in its environs, largely derived from the Mercian dialect of Old English, becoming the standard written form, rather than that of West Saxon areas such as Hampshire, Wiltshire and Somerset.
The Normans had a strong influence on English personal names. Old English names such as Alfred, Wulfstan, Aelfric, Harold, Godwin and Athelstan largely fell out of fashion, replaced by the likes of John, Peter and Simon, as well as Normanized Germanic names like William, Richard, Henry, Robert, Roger and Hugh.
Though the following list is in no way exhaustive, it illustrates some of the more common English words of French origin. Examples of French-to-English lexical contributions are classified by field and in chronological order. The periods during which these words were used in the English language are specified to the extent that this is possible.