# Dictionary Definition

stiffness

### Noun

1 the physical property of being inflexible and
hard to bend

2 the property of moving with pain or difficulty;
"he awoke with a painful stiffness in his neck"

3 the inelegance of someone stiff and unrelaxed
(as by embarrassment) [syn: awkwardness, clumsiness, gracelessness]

4 excessive sternness; "severity of character";
"the harshness of his punishment was inhuman"; "the rigors of boot
camp" [syn: severity,
harshness, rigor, rigour, inclemency, hardness]

# User Contributed Dictionary

## English

### Noun

#### Translations

inflexibility

- Finnish: taipumattomuus
- French: inflexibilité

- ttbc French: raideur
- ttbc German: Steifheit
- ttbc Interlingua: rigiditate, inflexibilitate
- ttbc Italian: rigidezza
- ttbc Portuguese: rigidez
- ttbc Spanish: tiesura, rigidez
- ttbc Dutch: Stijfheid

# Extensive Definition

- ''For pain and/or loss of range of motion of a joint, see joint stiffness

Stiffness is the resistance of an elastic
body to deflection or
deformation by an
applied force. It is an
extensive material property.

## Definition

The stiffness, k, of a body is- k=\frac

where

- P is the applied force
- δ is the deflected distance

As both the applied force and deflection
are vectors
(respectively P and δ), in general their relationship is
characterised by a stiffness matrix, k, where:

- P=k \delta \,

The deflection can, in general, refer to a point
distinct from that where the force is applied and a complicated
structure will not deflect purely in the same direction as an
applied force. The stiffness matrix enables such systems to be
characterised in straightforward terms.

The inverse of stiffness is compliance, typically
measured in units of metres per newton.

## Rotational stiffness

A body may also have a rotational stiffness, k,
given by

- k=\frac

where

- M is the applied moment
- θ is the rotation

In the SI system, rotational stiffness is
typically measured in newton-metres
per radian.

Further measures of stiffness are derived on a
similar basis, including:

## Relationship to elasticity

In general, elastic modulus is not the same as stiffness. Elastic modulus is a property of the constituent material; stiffness is a property of a solid body. That is, the modulus is an intensive property of the material; stiffness, on the other hand, is an extensive property of the solid body dependent on the material and the shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness is- k=\frac

where

- A is the cross-sectional area,
- E is the Young's modulus,
- L is the length of the element.

For the special case of unconstrained uniaxial
tension or compression, Young's
modulus of elasticity can be thought of as a measure of the
stiffness of a material.

## Use in engineering

The stiffness of a structure is of principal importance in many engineering applications, so the modulus of elasticity is often one of the primary properties considered when selecting a material. A high modulus of elasticity is sought when deflections are undesirable, while a low modulus of elasticity is required when flexibility is needed.stiffness in Catalan: Rigidesa

stiffness in German: Steifigkeit

stiffness in Spanish: Rigidez

stiffness in Italian: Rigidezza

stiffness in Japanese: 剛性

stiffness in Dutch: Stijfheid

stiffness in Portuguese: Rigidez

stiffness in Russian: Жёсткость

stiffness in Chinese: 剛度

# Synonyms, Antonyms and Related Words

adamantness, aridity, barrenness, bloodlessness, buckram, ceremonial, ceremoniousness,
ceremony, characterlessness,
cohesiveness,
colorlessness,
costliness, deadness, dearness, dignity, dismalness, dourness, dragginess, dreariness, dryness, dullness, durability, dustiness, effeteness, emptiness, etiolation, extrinsicality, firmness, flatness, flintiness, form, formality, formalization, fundamentalism, gravity, great cost, grimness, hard-bittenness,
hard-nosedness, hardiness, hardness, heaviness, highness, hollowness, immovability, immutability, impliability, inanity, inelasticity, inexcitability, inexorability, inflexibility, infrangibility, insipidity, insipidness, intransigeance, intransigence, intransigency, intransigentism,
irreconcilability,
jejunity, lastingness, leadenness, leatherlikeness,
lifelessness,
lowness of spirit, luxuriousness, obduracy, obdurateness, obstinacy, orthodoxy, paleness, pallor, pointlessness, pokiness, pomp, pomposity, ponderousness, precisianism, primness, purism, puritanism, relentlessness, renitence, renitency, resistance, richness, rigidity, rigidness, rigor, rigorism, rigorousness, ritual, rituality, ropiness, slowness, solemnity, spiritlessness, stamina, starchiness, steeliness, steepness, sterility, sternness, stiff temper,
stiltedness,
stodginess, strength, stringiness, stubbornness, stuffiness, stylization, sumptuousness, superficiality, tastelessness, tautness, tediousness, tenacity, tenseness, tension, tensity, tightness, toughness, unalterability, unbendingness, unbreakability, unbreakableness,
unchangeability,
uncompromisingness,
ungivingness,
uninterestingness,
unliveliness,
unrelentingness,
unyieldingness,
vapidity, vapidness, viscidity, vitality, weight, woodenness