definition of phase by The Free Dictionary




1. A distinct stage of development: “The American occupation of Japan fell into three successive phases” (Edwin O. Reischauer).

2. A temporary manner, attitude, or pattern of behavior: just a passing phase.

3. An aspect; a part: We must reconsider every phase of the operation.

4. Astronomy

a. One of the cyclically recurring apparent shapes of the visibly illuminated portion of the moon or a planet.

b. The relative configuration, measured in angular units such as degrees or radians, of two orbiting bodies that periodically eclipse.

5. Physics

a. A particular stage in a periodic process or phenomenon.

b. The fraction of a complete cycle elapsed as measured from a specified reference point and often expressed as an angle.

6. Chemistry

a. Any of the forms or states, solid, liquid, gas, or plasma, in which matter can exist, depending on temperature and pressure.

b. A discrete homogeneous part of a material system that is mechanically separable from the rest, as is ice from water.

7. Biology A characteristic form, appearance, or stage of development that occurs in a cycle or that distinguishes some individuals of a group: the white color phase of a weasel; the swarming phase of locusts.

tr.v. phased, phas·ing, phas·es

1. To plan or carry out systematically by phases.

2. To set or regulate so as to be synchronized.

Phrasal Verbs:

phase in

To introduce, one stage at a time.

phase out

To bring or come to an end, one stage at a time.


in phase

In a correlated or synchronized way.

out of phase

In an unsynchronized or uncorrelated way.

[Back-formation from New Latin phasēs, phases of the moon, from Greek phaseis, pl. of phasis, appearance, from phainein, to show; see bhā- in Indo-European roots.]

pha′sic (fā′zĭk) adj.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.




1. any distinct or characteristic period or stage in a sequence of events or chain of development: there were two phases to the resolution; his immaturity was a passing phase.

2. (Astronomy) astronomy one of the recurring shapes of the portion of the moon or an inferior planet illuminated by the sun: the new moon, first quarter, full moon, and last quarter are the four principal phases of the moon.

3. (General Physics) physics

a. the fraction of a cycle of a periodic quantity that has been completed at a specific reference time, expressed as an angle

b. (as modifier): a phase shift.

4. (General Physics) physics a particular stage in a periodic process or phenomenon

5. (General Physics) in phase (of two waveforms) reaching corresponding phases at the same time

6. (General Physics) out of phase (of two waveforms) not in phase

7. (Chemistry) chem a distinct state of matter characterized by homogeneous composition and properties and the possession of a clearly defined boundary

8. (Zoology) zoology a variation in the normal form of an animal, esp a colour variation, brought about by seasonal or geographical change

9. (Biology) biology (usually in combination) a stage in mitosis or meiosis: prophase; metaphase.

10. (Electrical Engineering) electrical engineering one of the circuits in a system in which there are two or more alternating voltages displaced by equal amounts in phase (sense 5). See also polyphase1

11. (Grammar) (in systemic grammar) the type of correspondence that exists between the predicators in a clause that has two or more predicators; for example connection by to, as in I managed to do it, or -ing, as in we heard him singing

vb (tr)

12. (often passive) to execute, arrange, or introduce gradually or in stages: a phased withdrawal.

13. (sometimes foll by with) to cause (a part, process, etc) to function or coincide with (another part, process, etc): he tried to phase the intake and output of the machine; he phased the intake with the output.

14. (Commerce) chiefly US to arrange (processes, goods, etc) to be supplied or executed when required

[C19: from New Latin phases, pl of phasis, from Greek: aspect; related to Greek phainein to show]

ˈphaseless adj

ˈphasic, ˈphaseal adj

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014



n., v. phased, phas•ing. n.

1. any of the major appearances or aspects in which a thing of varying modes or conditions manifests itself; facet.

2. a stage in a process of change or development.

3. a side, aspect, or point of view.

4. a state of synchronous operation.


a. the particular appearance presented by the moon or a planet at a given time.

b. one of the recurring appearances or states of the moon or a planet in respect to the form, or the absence, of its illuminated disk.

7. a mechanically separate, homogeneous part of a heterogeneous system, as a solution: liquid, solid, and gaseous phases.

8. Physics.

a. a particular stage or point of advancement in a cycle of motion or change.

b. the fractional part of the cycle that has elapsed, measured from a fixed datum.


9. to schedule or order so as to be available when or as needed.

10. to put in phase; synchronize.

11. phase down, to reduce or diminish by gradual stages.

12. phase in, to put or come into use gradually.

13. phase out, to bring or come to an end gradually; ease out of service.

[1805–15; (n.) back formation from phases, pl. of phasis phásis appearance =pha- (base of phaínein to show) + -sis -sis]

pha′sic, adj.

Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

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