phase

1 of 2

noun

ˈfāz 

1

: a particular appearance or state in a regularly recurring cycle of changes

phases of the moon

2

a

: a distinguishable part in a course, development, or cycle

the early phases of her career

b

: an aspect or part (as of a problem) under consideration

3

: the point or stage in a period of uniform circular motion, harmonic motion, or the periodic changes of any magnitude varying according to a simple harmonic law to which the rotation, oscillation, or variation has advanced from its standard position or assumed instant of starting

4

: a homogeneous, physically distinct, and mechanically separable portion of matter present in a nonhomogeneous physicochemical system

5

: an individual or subgroup distinguishably different in appearance or behavior from the norm of the group to which it belongs

also : the distinguishing peculiarity

phasic

ˈfā-zik 

adjective

phase

2 of 2

verb

phased; phasing

transitive verb

1

: to adjust so as to be in a synchronized condition

2

: to conduct or carry out by planned phases

3

: to introduce in stages

—usually used with in

phase in new models

Phrases

in phase

: in a synchronized or correlated manner

out of phase

: in an unsynchronized manner : not in correlation

Did you know?

Phase and Faze

Phase and faze are homophones (words pronounced alike but different in meaning, derivation, or spelling) that may easily be confused. Despite the similarity in pronunciation, these words bear little semantic resemblance to one another.

Although phase can function as a verb – it is found especially in combinations such as phase out, phase in, and phase into, meaning “to end, begin, etc. in phases” – the word is most commonly encountered as a noun, in which it typically carries a meaning related to steps in a process, cycles, or stages of development (as in “phases of the moon”).

Faze is generally used only as a verb, and means “to daunt or disconcert.” It often appears in negative expressions such as “it didn’t faze her a bit” or “nothing fazes him.”

Synonyms

Noun

• aspect
• side
• hand

Examples of phase in a Sentence

Noun

The project will be done in three phases.

He's in the final phase of treatment now.

The building project marks a new phase in the town's development.

He has been throwing tantrums a lot, but the doctor says it's just a phase.

a calendar based on the phases of the moon

Recent Examples on the Web

Noun

This next phase of the process is optional, but both Tretyakova and Sokolowski recommend it for maximum odor reduction. —Taylor Tobin, Southern Living, 30 Oct. 2025

Attack People with narcissism often transition into the attack phase next, pummeling the character and credibility of their loved one. —Angela Haupt, Time, 30 Oct. 2025

Verb

The change was slated to take effect immediately when the law was signed in July, but states are still awaiting federal guidance on when to stop or phase it out. —Renuka Rayasam, ABC News, 30 Oct. 2025

The word of caution didn’t phase her—at least, not at first. —Emma Burleigh, Fortune, 29 Oct. 2025

Word History

Etymology

Noun

New Latin phasis, from Greek, appearance of a star, phase of the moon, from phainein to show (middle voice, to appear) — more at fancy

First Known Use

Noun

1647, in the meaning defined at sense 1

Verb

1904, in the meaning defined at sense 1

Phrases Containing phase

• color phase
• L-phase
• M phase
• phase-contrast
• phase-contrast microscope
• phase down
• phase in
• phase modulation
• phase out
• single-phase
• S phase
• sub-phase
• three-phase
• two-phase

Rhymes for phase

• baize
• bays
• blase
• blaze
• braes
• braze
• chaise
• claes
• clays
• craze
• dais
• days

Kids Definition

phase

1 of 2 noun

ˈfāz 

1

: a particular appearance or state in a repeating series of changes

phases of the moon

2

: a step or part in a series of events or actions : stage

3

: a particular part or feature (as of an activity, situation, or a subject being considered) : aspect

4

: a physically different portion or kind of matter present in a mixed system

the three phases ice, water, and steam

phase

2 of 2 verb

phased; phasing

1

: to do in steps according to a plan

2

: to introduce in stages

—usually used with in

phase in new models

Medical Definition

phase

noun

ˈfāz 

1

: a particular appearance or state in a regularly recurring cycle of changes

2

: a distinguishable part in a course, development, or cycle

the early phases of a disease

3

: a point or stage in the period of a periodic motion or process (as a light wave or a vibration) in relation to an arbitrary reference or starting point in the period

4

: a homogeneous, physically distinct, and mechanically separable portion of matter present in a nonhomogeneous physicochemical system

especially : one of the fundamental states of matter usually considered to include the solid, liquid, and gaseous forms

5

: an individual or subgroup distinguishably different in appearance or behavior from the norm of the group to which it belongs

also : the distinguishing peculiarity