strain

strain: see strength of materials.

---

strain

In the physical sciences and engineering, a number that describes the relative deformation of elastic, plastic, and fluid materials under applied forces. It arises throughout the material as the particles of the material are displaced from their usual position. Normal strain is caused by forces perpendicular to planes or cross sections of the material, such as in a volume that is under pressure on all sides. Shear strain is caused by forces that are parallel to, and lie in, planes or cross sections, such as in a short metal tube that is twisted about its longitudinal axis. See also deformation and flow.

---

strain¹

1. Music a theme, melody, or tune

2. a feeling of tension and tiredness resulting from overwork, worry, etc.; stress

3. a particular style or recurring theme in speech or writing

4. Physics the change in dimension of a body under load expressed as the ratio of the total deflection or change in dimension to the original unloaded dimension. It may be a ratio of lengths, areas, or volumes

---

strain²

1. a group of organisms within a species or variety, distinguished by one or more minor characteristics

2. a variety of bacterium or fungus, esp one used for a culture

---

strain [strān]

(biology)

An intraspecific group of organisms that possess only one or a few distinctive traits and are maintained as an artificial breeding group.

(cell and molecular biology)

A population of cells derived either from a primary culture or from a cell line by the selection or cloning of cells having specific properties or markers.

(mechanics)

Change in length of an object in some direction per unit undistorted length in some direction, not necessarily the same; the nine possible strains form a second-rank tensor.