What does "phase" mean?

1. (a stage in a process) one part of a process or a stage in someone's development. 2. (astronomy) the changing shape of the bright part of the moon or a planet. 3. (chemistry/physics) a state of matter, such as being a solid, liquid, or gas. 4. (physics/waves) a specific point in a repeating movement, like a wave or vibration. 5. (to introduce or remove gradually) to start or stop something in gradual steps rather than all at once.

How do you use "phase"?

Usually functions as a phrasal verb: 'phase in' or 'phase out'.

phase

n. · v.

US //ˈfeɪz// UK //fˈeɪz// phase

1 a stage in a process (n.)
B2 Upper Intermediate General-service

one part of a process or a stage in someone's development.

a distinguishable stage in a sequence of events or a period of development.

Example

Most teenagers go through a phase where they want to be alone in their rooms.

Example

The first phase of the construction project involves clearing the site and laying the foundation before the winter weather sets in.
2 astronomy (n.)
B2 Upper Intermediate Technical Science

the changing shape of the bright part of the moon or a planet.

the particular appearance of a celestial body's illuminated disk in a recurring cycle.

Example

The moon is in its crescent phase tonight.

Example

Astronomers track the lunar phases to predict tidal patterns and optimal conditions for deep-space observation.
- appearance
- aspect

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3 chemistry/physics (n.)
C1 Advanced Academic Technical Science

a state of matter, such as being a solid, liquid, or gas.

a physically distinctive form of matter, such as a solid, liquid, gas, or plasma.

Example

When water boils, it changes from a liquid phase to a gas phase.

Example

The experiment demonstrated how the substance remains stable in its solid phase even under extreme atmospheric pressure.
- state
- form
4 physics/waves (n.)
C1 Advanced Academic Technical Science

a specific point in a repeating movement, like a wave or vibration.

the position of a point in time on a waveform cycle.

Example

If two sound waves are out of phase, they can cancel each other out.

Example

The engineers adjusted the signal timing to ensure the two oscillators remained in phase, preventing destructive interference.
- position
- timing
5 to introduce or remove gradually (v.)
B2 Upper Intermediate

to start or stop something in gradual steps rather than all at once.

to introduce or withdraw something in planned stages; typically used with 'in' or 'out'.

Example

The company will phase out the old software over the next six months.

Example

The government plans to phase in the new tax regulations over a three-year period to minimize the economic impact on small businesses.

Usage

Usually functions as a phrasal verb: 'phase in' or 'phase out'.

Etymology 1

From New Latin phasis, from Ancient Greek φάσις (phásis, “an appearance”), from φαίνω (phaínō, “to cause to appear”); compare phantasm and see face.

Etymology 2

From Latin phase (“passover”), Phasa, from Hebrew פָּסַח (pésach).