# length

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## length

1. Prosody Phonetics the metrical quantity or temporal duration of a vowel or syllable
2. the distance from one end of a rectangular swimming bath to the other
3. Prosody the quality of a vowel, whether stressed or unstressed, that distinguishes it from another vowel of similar articulatory characteristics. Thus in English beat is of greater length than in English bit
4. Cricket the distance from the batsman at which the ball pitches
5. Bridge a holding of four or more cards in a suit

## Length

A one-dimensional extension in space. Length is one of the three fundamental physical quantities, the others being mass and time. It can be measured by comparison with an arbitrary standard; the specific one in most common usage is the international meter. In 1983, at the meeting of the Conférence Général des Poids et Mésures, the meter was redefined in terms of time and the speed of light: “The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” This definition defines the speed of light to be exactly 299 792 458 m/s, and defines the meter in terms of the most accurately known quantity, the second. See Light, Mass, Time

## Length

a numerical characteristic of the extent of curves. The concept of length is defined differently for different cases. (1) The length of a line segment is the distance between its end points, measured by some segment taken as a unit of length. (2) The length of a polygonal line is the sum of the lengths of its components. (3) The length of a simple arc is the limit of the lengths of polygonal lines inscribed in the arc, when the number of components increases indefinitely and the maximum length of the components tends to zero. (4) The length of a continuous curve consisting of a finite number of simple arcs is equal to the sum of the lengths of these arcs. For example, the circumference of a circle can be obtained as the limit of the perimeters of inscribed regular polygons when the number of their sides is doubled indefinitely; it is equal to 2πR where R is the radius of the circle. Any continuous curve has finite or infinite length. If its length is finite, then the curve is said to be rectifiable. The graph (see Figure 1) of the function

for 0 <x ≤ 1 and f(x) = 0 when x = 0 is an example of a nonrectifiable curve; here the lengths of the inscribed polygonal lines increase beyond all bound as the length of the components tend to zero. If the equation of a plane curve has the form y =f(x) (a ^ x ^ b)m rectangular coordinates and the function f(x) has a continuous derivative f’(x), then the length of the curve is given by the integral

The length of a curve given in parametric form and the length of a space curve can be expressed in a similar manner.

Figure 1

To calculate the length of a curve the mathematicians of antiquity essentially used lengths of polygonal lines and passage to the limit. For them, however, such passage to the limit was only a method for calculating the length of a curve and not for defining the concept of the length of a curve, since they apparently perceived the latter as one of the elementary mathematical concepts. The necessity of defining the length of a curve became clear only in the first half of the 19th century. A full elucidation of the problem was achieved by C. Jordan. In differential geometry the length of a curve is also defined on a surface or in an arbitrary Riemannian space.

### REFERENCES

Lebesgue, H. Ob izmerenii velichin, 2nd ed. Moscow, 1960. (Translated from French.)
Fikhtengol’ts, G. M. Kurs differentsial’nogo i integral’nogo ischisleniya, 7th ed. vol. 2. Moscow, 1969.

## length

[leŋkth]
(mechanics)
Extension in space.
References in periodicals archive ?
The role of routine cervical length screening in selected high-and low-risk women for preterm birth prevention.
All of the sonographers participating in the study were Cervical Length Education and Review (CLEAR) certified, and the institution's lead sonographer carried out a ongoing quality assurance program.
Our results suggested that cervical cerclage could prolong gestational weeks more effectively than vaginal progesterone for women who had at least one prior PTB and an asymptomatic shortened cervical length detected by ultrasound examination in the second trimester.
Further, there is presently no data to support the use of progesterone in asymptomatic patients with a cervical length greater than 20 mm even in the context of tobacco.
Physical examination aided by sonographic evaluation of cervical length can help in the diagnosis.
As has been pointed out by Leitich et al (5), mean cervical length, in addition to showing intersubject variability, appears to vary with ethnic identity.
While my physician used tools like testing cervical length and prescribing progesterone shots, it was important to both my husband and I that we wouldn't be surprised like we had been with Ryan's early delivery.
The purpose of our study was to assess changes in cervical length during physiologic pregnancy, establish regression models and construct reference ranges that could be used at any gestational period for prompt identification of women with changes in cervical length.
The predictive accuracies of abnormal cervical length and of the presence of fibronectin are depicted in the Figure.
in women with singleton gestations, no prior history of PTB, and a short cervical length ([less than or equal to] 20 mm at [less than or equal to] 24 weeks) vaginal progesterone can be offered In October of 2012, ACOG published its own recommendations regarding the prevention of PTB.
WASHINGTON -- Universal cervical length screening to prevent preterm birth has been implemented by more two-thirds of institutions with maternal-fetal medicine fellowship programs, but less than half of these programs screen with transvaginal ultrasound, a national survey has found.

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