phase

American  

[feyz] / feɪz /

noun

• phases
  plural

1. any of the major appearances or aspects in which a thing of varying modes or conditions manifests itself to the eye or mind.

   Synonyms:

   side, facet, shape, form

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

   Each phase of life brings its own joys.

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

   This is only one phase of the question.

4. a state of synchronous operation.

   to put two mechanisms in phase.

5. Astronomy.

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

   2. 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.

      the phases of the moon.

6. Zoology. color phase.

7. Chemistry. a mechanically separate, homogeneous part of a heterogeneous system.

   the solid, liquid, and gaseous phases of a system.

8. Physics. a particular stage or point of advancement in a cycle; the fractional part of the period through which the time has advanced, measured from some arbitrary origin often expressed as an angle phase angle, the entire period being taken as 360°.

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verb (used with object)

• phases,
  present (3rd person singular)
• phased,
  past participle,  past
• phasing
  present participle

1. to schedule or order in gradual stages, so as to be available when or as needed.

2. Physics. to adjust the phase of (an electrical or mechanical device), especially to synchronize it with that of one or more other devices.

   a properly phased, synchronous pulse generator that augments the action of the human heart.

verb phrase

1. phase in to put or come into use gradually; incorporate by degrees.

   to phase in new machinery.

2. phase down to reduce by gradual stages.

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

   to phase out obsolescent machinery.

phase British  

/ feɪz /

noun

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 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. physics

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

   2. ( as modifier )

      a phase shift

4. physics a particular stage in a periodic process or phenomenon

5. (of two waveforms) reaching corresponding phases at the same time

6. (of two waveforms) not in phase

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

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

9. biology (usually in combination) a stage in mitosis or meiosis

   prophase

   metaphase

10. 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 polyphase

11. (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

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verb

1. (often passive) to execute, arrange, or introduce gradually or in stages

   a phased withdrawal

2. (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

3. to arrange (processes, goods, etc) to be supplied or executed when required

phase Scientific  

/ fāz /

1. Any of the forms, recurring in cycles, in which the Moon or a planet appears in the sky.

2. One of a set of possible homogenous, discrete states of a physical system. States of matter such as solid and liquid are examples of phases, as are different crystal lattice structures in metals such as iron.

3. See also phase transition state of matter

4. A measure of how far some cyclic behavior, such as wave motion, has proceeded through its cycle, measured in degrees or radians. At the beginning of the phase, its value is zero; at one quarter of its cycle, its phase is 90 degrees (π/2 radians); halfway through the cycle its value is 180 degrees (π radians), and so on.

5. ◆ The phase angle between two waves is a measure of their difference in phase. Two waves of the same frequency that are perfectly in phase have phase angle zero; if one wave is ahead of the other by a quarter cycle, its phase angle 90 degrees (π/2 radians); waves that are perfectly out of phase have phase angle 180 degrees (π radians), and so on.

6. See more at wave

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Other Word Forms

Derived Forms

• subphase
  noun
• rephase
  verb (used with object)
• phaseal
  adjective
• phaseless
  adjective
• phasic
  adjective
• unphased
  adjective

Inflected Forms

Nouns

• phases
  plural

Participles

• phasing
  present
• phased
  past

Conjugated Forms

Present

• phase
  simple
• phases
  simple
• have phased
  perfect
• has phased
  perfect
• am phasing
  progressive
• are phasing
  progressive
• is phasing
  progressive
• have been phasing
  perfect progressive
• has been phasing
  perfect progressive

Past

• phased
  simple
• had phased
  perfect
• was phasing
  progressive
• were phasing
  progressive
• had been phasing
  perfect progressive

Future

• will phase
  simple
• will have phased
  perfect
• will be phasing
  progressive
• will have been phasing
  perfect progressive

Etymology

Origin of phase

First recorded in 1805–15; (noun) back formation from phases, plural of phasis

Explanation

A phase is a particular period of time, like someone whose "teenage rebellion" phase lasts well into her thirties. The word phase can mean a stage in a person’s development or a step in a process, such as “the next phase in the Interstate 57 project.” Phase can also be a verb, usually followed by in or out, to mean slowly introducing or getting rid of something. For example, your school might phase in a new rule or phase out an old one, as new students arrive.

Example Sentences

See Examples For:

phase phases phased phasing

RAV4 production increases from end-2026 onward alongside its main customer also entering an expansionary output phase could benefit the Japanese automotive parts manufacturer further, Yoshida says.

From The Wall Street Journal ● Aug. 20, 2026

"The mechanism responsible for the emergence of this second phase has long been debated, and our approach provides a powerful new way to uncover the hidden physics behind phase transitions in quantum materials," Gedik says.

From Science Daily ● Aug. 20, 2026

Understanding how the two waves appear and coexist could provide clues about the more complicated phase transitions involved in superconductivity and other unusual electronic states.

From Science Daily ● Aug. 20, 2026

"The next phase of the industry is less about demonstrating that a robot can walk and more about demonstrating that it can perform economically useful tasks," Morningstar equity analyst Kangyuxiao Li told AFP.

From Barron's ● Aug. 19, 2026

And he’d walked onto Wall Street at the very beginning of a curious phase.

From "The Big Short" by Michael Lewis

Zach Keeling, Sapporo USA CEO, said in a statement that Sapporo USA is winding down the Escondido brewery in phases because it has “not yet found a viable long-term solution” for the site.

From Los Angeles Times ● Aug. 21, 2026

The drills reportedly consist of two phases: the first, focused on defending against potential North Korean threats, was due to run until Friday.

From Barron's ● Aug. 21, 2026

"Our experiment provides a very neat way to study these multiple phases."

From Science Daily ● Aug. 20, 2026

The researchers wanted to study a material in which two CDW phases exist at the same time.

From Science Daily ● Aug. 20, 2026

Soon after he arrived in Florence, Galileo discovered the phases of Venus, changes in its appearance similar to the phases of the Moon, and these changes could only be explained if Venus orbits the Sun.

From "The Scientists" by John Gribbin

This included three scenarios: a full closure, a partial closure over a period of five years and a limited series of phased closures, sources close to the situation told the AP, asking to remain anonymous.

From Los Angeles Times ● Aug. 13, 2026

If such a proposal was phased in, people would have time to adjust their planning, Butler said.

From MarketWatch ● Aug. 3, 2026

In addition to a 15-point roadmap published by the US-led Board of Peace, the BBC has seen a four-page plan for the phased disarmament of Hamas and gradual Israeli withdrawal.

From BBC ● Jul. 31, 2026

Earlier, a diplomatic source told AFP that the roadmap "offers a balanced and pragmatic path forward, with all weapons decommissioned and a phased transition of responsibilities" to the new authorities.

From Barron's ● Jul. 31, 2026

It made my lungs feel heavy, my heart grow light, until the juxtaposition of the two phased into sleep.

From "The Marrow Thieves" by Cherie Dimaline

Among them is Syngenta, a Swiss-based company owned by the Chinese government that was one of paraquat’s largest manufacturers, which said it was phasing out the product globally for commercial reasons.

From Los Angeles Times ● Aug. 11, 2026

In its report, published on Wednesday, external, the committee recommended phasing in a retirement age of 80 and requiring members to attend at least 20% of sitting days.

From BBC ● Jul. 15, 2026

Starting today, the federal government will put new limits on certain types of borrowing, begin phasing out longstanding repayment programs and launch a new one.

From MarketWatch ● Jul. 1, 2026

With Qantas rolling out its ultra-long-haul services on more proven and profitable routes, Seow thinks the planned phasing de-risks the early stages of the project.

From The Wall Street Journal ● Jun. 19, 2026

He seemed in a state of constant transition, phasing in and out of dimensions, unsure whether to be my father’s son or his wife’s husband.

From "Educated" by Tara Westover

Related Words

• aspect
• chapter
• development
• point
• stage
• state
• step
• time