Дюйм: единица измерения длины

Unit of length

The inch (symbol: in or ) is a unit of length in the British Imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth"), the word inch is also sometimes used to translate similar units in other measurement systems, usually understood as deriving from the width of the human thumb. Standards for the exact length of an inch have varied in the past, but since the adoption of the international yard during the 1950s and 1960s the inch has been based on the metric system and defined as exactly 25.4mm.

The English word "inch" was an early borrowing from Latin uncia ("one twelfth; Roman inch; Roman ounce"). The vowel change from Latin to Old English (which became Modern English ) is known as umlaut. The consonant change from the Latin (spelled c) to English is palatalisation. Both were features of Old English phonology; see and for more information. "Inch" is cognate with "ounce" , whose separate pronunciation and spelling reflect its reborrowing in Middle English from Anglo Norman unce and ounce. In many other European languages, the word for "inch" is the same as or derived from the word for "thumb", as a man's thumb is about an inch wide (and this was even sometimes used to define the inch). In the Dutch language a term for inch is engelse duim (english thumb). Examples include ("inch") and polze ("thumb"); ("thumb"); Danish and tomme ("inch") tommel ("thumb"); duim (whence and дюйм); ; , hüvelyk; ; polegada ("inch") and polegar ("thumb"); ("duim"); ("thumb"); lang es ("inch") and pulgar ("thumb"); and tum ("inch") and tumme ("thumb").

The inch is a commonly used customary unit of length in the United States, Canada, and the United Kingdom. and may continue to be used as a secondary or supplementary indication following a metric measurement for other purposes.

Inches are used for display screens (e. g. televisions and computer monitors) worldwide. It is the official Japanese standard for electronic parts, especially display screens, and is the industry standard throughout continental Europe for display screens (Germany being one of few countries to supplement it with centimetres in most stores). Inches are commonly used to specify the diameter of vehicle wheel rims, and the corresponding inner diameter of tyres in tyre codes.

Both inch based and millimeter based hex keys are widely available for sale in Europe.

The international standard symbol for inch is in (see ISO 31 1, Annex A) but traditionally the inch is denoted by a double prime, which is often approximated by a double quote symbol, and the foot by a prime, which is often approximated by an apostrophe. For example; three feet, two inches can be written as 3 2. (This is akin to how the first and second "cuts" of the hour are likewise indicated by prime and double prime symbols, and also the first and second cuts of the degree.) Subdivisions of an inch are typically written using dyadic fractions with odd number numerators; for example, two and three eighths of an inch would be written as and not as 2.375 nor as However, for engineering purposes fractions are commonly given to three or four places of decimals and have been for many years.

Before the adoption of the metric system, several European countries had customary units whose name translates into "inch". The French pouce measured roughly 27.0 mm, at least when applied to describe the calibre of artillery pieces. The Amsterdam foot (voet) consisted of 11 Amsterdam inches (duim). The Amsterdam foot is about 8% shorter than an English foot.

The now obsolete Scottish inch (òirleach), of a Scottish foot, was about 1.0016 imperial inches (about ).