ISBN 0-203-40372-X. Ringe, Don (2006). From Proto-Indo-European to Proto-Germanic (PDF). A Linguistic History of English (1st ed.). New York City: Oxford University In linguistics, grammatical number is a feature, in many languages, of nouns, pronouns, adjectives and verb agreement that expresses count distinctions (such as "one", "two" or "three or more"). English and many other languages present number categories of singular or plural. Some languages also have a dual, trial and paucal number or other arrangements. The word "number" is also used in linguisti Dual number existed in all nouns and adjectives of Proto-Indo-European around 4000 BCE, and was inherited in some form in many of its prehistoric, protohistoric, ancient, and medieval descendents. Only rarely has it persisted in Indo-European languages to the modern day. It survived in Proto-Germanic in the first and second person pronouns, where it was then inherited by Old English, Old High German, Old Low German, Early Old Swedish, Old Norwegian, Old Icelandic, and Gothic. It continued in Icelandic until the 1700s, some dialects of Faroese until at least the late 1800s, and some dialects of North Frisian through the 1900s. From Proto-Greek it entered Ancient Greek, and from Proto-Indo-Iranian it entered Sanskrit. From Proto-Slavic, it still exists today in Slovene and the Sorbian languages. Indo-European languages that have long ago lost the dual still sometimes have residual traces of it, such as the English distinctions both vs. all, either vs. any, and neither vs. none. The Norwegian både, cognate with English both, has further evolved to be able to refer to more than two items, as in både epler, pærer, og druer, literally "both apples, pears, and grapes."