Quantum Theory noun [U] ( physics ) a theory that based on the idea that energy can only be changed in units that cannot be divided.

**Quantum Physics **noun [U] the branch of science that investiges the principles of QUANTUM THEORY to understand the behaviour of PARTICLES at the ATOM and SUB-ATOM level

Quantum mechanics noun [U] ( physics ) the branch of MECHANICS that deals with movement and force in pieces of matter smaller than ATOMS

Quantum noun (plural quanta) ( physics ) a very small quantity of ELECTROMAGNETIC energy.

Quantum leap noun a sudden, great and import change, improvement or development

Particle physics noun [U] the scientific study of very small pieces of matter that are parts of an ATOM

**Particle noun **:

1. a very small piece of sth. : particle of gold/dust see also ALPHA PARTICLE, BETA PARTICLE, ELEMENTARY PARTICLE, SUBATOMIC PARTICLE
2. ( grammar ) an adverb or a preposition that can combine with a verb to make a phrase verb: _In 'She tore up the letter', the word 'up' is a particle.

Elementary particle ( also fundamental particle ) noun ( physics ) a very smallpiece of MATTER ( = a substance ), such as a QUARK, that doesn't contain within it any even smaller pieces of matter => compare SUBATOMIC PARTICLE

Substance noun:

1. a type of solid, liquid or gas that has particular qualities: a sticky substance | a chemical/radioactive/hazardous substance | _Some frogs produce toxic substance in their skin. _
2. [C] a drug, especially an illegal one: _ banned/illegal/controlled substances | substance use _
3. [U] the quality of being based on facts or the truth: _The commission's report gives substance to these allegations. _ | _There is some substance in what he says. | without ~ _It was malicious gossip, completely without substance.
4. [U] The most important or main part of sth: the ~ of sth Love and guilt from the substance of his new book. | in ~ I agreed with what she said in substance, though not with every detail.
5. [U] ( formal ) important **SYN: significance: of ~ ** matters of substance | _Nothing of any substance was achieved in the meeting.
6. IDM a man/woman of substance ( formal ) a rich and powerful man or woman

Subatomic particle noun ( physics ) a very small piece of MATTER, such as an ELECTRON or a PROTON, that is smaller than an ATOM => compare ELEMENTARY PARTICLE

atom noun the smallest PARTICLE of a chemical element that can exist: the splitting of the attom | Two atoms of hydrogen combine with one atom of oxygen to form a molecular of water.** => WORDFINDER NOTE** at PHYSICS
WORDFINDER antiparticle, electron, ion, neutron, nucleus, particle, positron, proton, valency