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Oscillate vs. Vacillate: What's the Difference?

Edited by Aimie Carlson || By Janet White || Updated on September 28, 2023
"Oscillate" refers to moving back and forth at a regular interval, while "Vacillate" denotes indecision, waver between different opinions or actions.

Key Differences

Oscillate" and "Vacillate" are both verbs that denote a form of movement or fluctuation. However, their nuances and contexts distinctly separate them.
"Oscillate" primarily pertains to a physical movement, usually a repetitive and regular back-and-forth motion. For example, a pendulum in a grandfather clock oscillates. Contrarily, "Vacillate" encapsulates an internal, mental wavering, such as when a person cannot decide between two choices.
One can visualize "Oscillation" by observing the motion of a fan, where the blades move to and fro in a consistent manner. "Vacillation", however, is more abstract, seen when someone is torn between two jobs and keeps changing their mind.
In essence, "Oscillate" is predominantly about tangible, rhythmic motion, while "Vacillate" paints a picture of uncertainty and continual change of mind.
Despite both words hinting at some form of alternation, "Oscillate" captures a predictable, regular pattern, whereas "Vacillate" speaks to unpredictability rooted in indecision.

Comparison Chart


Movement in a to-and-fro motion
Waver between different opinions or actions


Typically physical motion
Usually pertains to mental indecision

Usage Example

A swing oscillates back and forth
She vacillated between the two job offers


Predictable, rhythmic
Unpredictable, uncertain


Repetitive motion
Indecision, flip-flopping

Oscillate and Vacillate Definitions


Produce or modulate waves.
The radio tower oscillated a powerful signal.


Be indecisive.
She tended to vacillate when faced with tough decisions.


Vary between two levels, states, or opinions.
His moods oscillated between joy and despair.


Waver between different opinions or actions.
He vacillated between accepting or declining the offer.


Move or swing back and forth.
The metronome oscillated at a steady beat.


Alternate or waver between states.
His feelings vacillated between hope and despair.


Fluctuate in magnitude or position.
The stock prices oscillated throughout the day.


Change one's mind repeatedly.
Politicians often vacillate on controversial issues.


Alternate between extremes.
Temperatures oscillated around the freezing point.


Show uncertainty or hesitation.
The committee vacillated on the proposal's merits.


To swing back and forth with a steady, uninterrupted rhythm.


To be unable to choose between different courses of action or opinions; waver
She vacillated about whether to leave.


To waver, as between conflicting opinions or courses of action; vacillate
"The court has oscillated over the decades from more liberal to less, more conservative to less, depending upon who was president at the time of vacancies" (Gordon J. Humphrey).


To change between one state and another; fluctuate
The weather vacillated between sunny and rainy.


(Physics) To vary between alternate extremes, usually within a definable period of time.


(Archaic) To sway from one side to the other.


(intransitive) To swing back and forth, especially if with a regular rhythm.
A pendulum oscillates slower as it gets longer.


(intransitive) To sway unsteadily from one side to the other; oscillate.


(intransitive) To vacillate between conflicting opinions, etc.
The mood for change oscillated from day to day.


(intransitive) To swing indecisively from one course of action or opinion to another.


(intransitive) To vary above and below a mean value.


To move one way and the other; to reel or stagger; to waver.
[A spheroid] is always liable to shift and vacillatefrom one axis to another.


To move backward and forward; to vibrate like a pendulum; to swing; to sway.


To fluctuate in mind or opinion; to be unsteady or inconstant; to waver.


To vary or fluctuate between fixed limits; to act or move in a fickle or fluctuating manner; to change repeatedly, back and forth.
The amount of superior families oscillates rather than changes, that is, it fluctuates within fixed limits.


Be undecided about something; waver between conflicting positions or courses of action;
He oscillates between accepting the new position and retirement


Be undecided about something; waver between conflicting positions or courses of action;
He oscillates between accepting the new position and retirement


Move or sway in a rising and falling or wavelike pattern;
The line on the monitor vacillated


Move or swing from side to side regularly;
The needle on the meter was oscillating


Can "Oscillate" be used in non-physical contexts?

Yes, it can refer to fluctuating between states or opinions but is distinct from vacillate's indecision.

Can a person "Oscillate"?

Physically, yes, as in moving back and forth. Mentally, it means fluctuating between states.

Are "Oscillate" and "Vacillate" interchangeable?

No, "Oscillate" refers to physical movement, while "Vacillate" means to waver mentally.

Is "Vacillate" always about indecision?

Primarily, but it can also imply a general back-and-forth change.

Is the movement of "Oscillate" predictable?

Typically, it's a regular and rhythmic motion.

Is "Vacillate" always negative?

Not necessarily, but it often carries a connotation of indecision.

Why might someone "Vacillate" on a decision?

Due to uncertainty, lack of information, or emotional conflict.

Can objects "Vacillate"?

Not in the typical sense; it's mainly used for individuals or groups with decision-making capabilities.

How is "Vacillate" different from "hesitate"?

"Vacillate" is about changing one's mind; "hesitate" is pausing before making a decision.

Can "Vacillate" refer to physical movement?

It's rare and typically denotes a wavering, uncertain movement.

How does a pendulum "Oscillate"?

It swings back and forth in a consistent rhythm.

Can a market "Oscillate"?

Yes, it can fluctuate or vary in performance or value.

Is "Vacillate" used in formal contexts?

Yes, it's suitable for both formal and informal settings.

How does "Oscillate" relate to electronics?

Devices can oscillate electrical signals at specific frequencies.

Can feelings "Oscillate"?

Yes, feelings can fluctuate or alternate between different states.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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