# Particle

In the physical sciences, a particle is a small localized object to which can be ascribed several physical properties such as volume or mass. The word is rather general in meaning, and is refined as needed by various scientific fields. Something that is composed of particles may be referred to as particulate, although this term is generally used to refer to a suspension of unconnected particles, rather than a connected particle aggregation.

Whether objects can be considered particles depends on the scale of the context; if an object's own size is small or negligible, or if geometrical properties and structure are irrelevant, then it can be considered a particle. For example, grains of sand on a beach can be considered particles because the size of one grain of sand (~1 mm) is negligible compared to the beach, and the features of individual grains of sand are usually irrelevant to the problem at hand. However, grains of sand would not be considered particles if compared to buckyballs (~1 nm).

### Other articles related to "particle, particles":

Non-Relativistic Quantum Free Particle - Measurement and Calculations
... conjugate, over all space is the probability of finding the particle in all space, which must be unity if the particle exists This is the normalization condition for the wave function ... In the limit ħ → 0, the particle's position and momentum become known exactly ... Interpretation of wave function for one spin-0 particle in one dimension ...
Classical Free Particle
... The classical free particle is characterized simply by a fixed velocity v ... by and the kinetic energy (equal to total energy) by where m is the mass of the particle and v is the vector velocity of the particle ...
Free Particle
... In physics, a free particle is a particle that, in some sense, is not bound by an external force, or equivalently not in a region where its potential energy varies ... In classical physics, this means the particle is present in a "field-free" space ...
... Consider a massless relativistic particle approaching a potential step of height with energy and momentum ... The particle's wave function, follows the time-independent Dirac equation And is the Pauli matrix Assuming the particle is propagating from the left, we ... cannot reverse the direction of the group velocity of a massless relativistic particle ...
Distribution of Particles
... Colloidal particles are the components of a colloid ... The dispersed-phase particles have a diameter of between approximately 5 and 200 nanometers ... Soluble particles smaller than this will form a solution as opposed to a colloid ...

### Famous quotes containing the word particle:

You don’t hold any mystery for me, darling, do you mind? There isn’t a particle of you that I don’t know, remember, and want.
Noël Coward (1899–1973)

Each particle is a microcosm, and faithfully renders the likeness of the world.
Ralph Waldo Emerson (1803–1882)

The way to learn German, is, to read the same dozen pages over and over a hundred times, till you know every word and particle in them, and can pronounce and repeat them by heart.
Ralph Waldo Emerson (1803–1882)