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Hypothetically Speaking vs. Theoretically Speaking: Differences and Usage

We have all heard the phrases hypothetically speaking and theoretically speaking and have even used them ourselves, but are we using them correctly? What then is the difference between hypothetically speaking and theoretically speaking? 

As adverbs, “hypothetically” and “theoretically” describe ways of speaking about particular assumptions or larger principles for the sake of discussion or argument. In the sciences, a “theory” is a set of principles and laws based on experimentation, while a “hypothesis” remains untested. As commonly used in laymen’s terms both “hypothetically” and “theoretically” often refer more to possibilities and concepts that may or may not apply in practice.

This article will explain how the two phrases differ in meaning and why we have come to use them interchangeably. 

Hypothetically Speaking vs. Theoretically Speaking

Hypothetically SpeakingTheoretically Speaking
Making an untested assumption.Making an assumption based on larger, accepted principles.

When you speak hypothetically, you’re posing a question or making an assumption in an attempt to explain something about the natural world. For instance, a scientist may ask a question in a hypothetical way to begin a discussion that leads to experimentation.

If the scientists are able to confirm something about the hypothetical question, they may begin to develop larger principles to explain that particular phenomenon. When dealing with larger principles, they are speaking theoretically.

What Is a Hypothesis?

“Hypothetically” is the adverb form of the noun “hypothesis,” so it will help to provide a clear definition of what a “hypothesis” is. 

Definition of Hypothesis

A hypothesis is essentially a guess or possible explanation we make based on limited information to begin a scientific investigation. It comes from a Greek word meaning “foundation” (source).

The scientist proposed the hypothesis that dolphins can speak using words. 

John’s hypothesis is that ducks swim faster than dogs.

Philosophers also use hypotheses as foundational ideas to help build larger axioms or accepted principles. First, they make a proposition without presuming it to be true or false. The hypothesis may develop into a larger principle after they’ve tested its validity.

The hypothesis that parallel worlds exist led to a passionate discussion.

Time travel is a hypothesis based on science fiction.

When you use the word “hypothetically,” you propose an idea or guess to begin a discussion or argument while imagining it as neither true nor untrue at that point (source).

Hypothetically, it’s possible people can fly, but I’ve never known it to happen. 

Hypothetically a tenth planet is possible.

What Is a Hypothetical Question?

A hypothetical question offers an opinion, personal belief, or hypothesis not yet rooted in facts. Instead, it deals with an action or scenario that might or might not happen as the questioner sets the framework for discussion (source). 

If you were a dinosaur, which one would you choose?

Suppose you won the Powerball, what would you do with all the money?

At this point, you may wonder what purpose a hypothetical question plays in your daily life. Hypothetical questions play a role in many fields, including literature, communication, and job interviews, not to mention our everyday conversations. 

For instance, hypothetical questions gain the readers’ opinions regarding a particular book and aid further discussions in a book club on literature. 

What do you suppose the ring symbolizes in the Lord of the Rings Trilogy?

What would you have done if you were the heroine of the story?

Employers use hypothetical questions as a means to screen potential employees.

What would you do to reprimand a member of your team?

How would you handle an angry customer?

What Hypothetical Means in Science

Scientists pose hypothetical questions when they speculate or guess how something works. To a scientist, a scientific hypothesis is the lowest step of the scientific method. 

A scientist poses what they refer to as an educated guess based on previous knowledge and observation. It includes an explanation of why they believe their guess is correct. 

Supposedly, a scientist never has a fixed outcome in mind. The hypothesis must be something that is either refutable or that they can support through experimentation and observation (source). 

There is a specific way one must state a hypothesis. The statement proposes the possibility or “if” and explains what may happen due to the possibility, the “then.” To clarify — If then, then that.

We also speak like this all the time when we make conclusions based on particular propositions.

If a dog eats human food every day, then they may never eat their kibble.

If children go to school with coconut oil in their hair, they may never have lice.

If fluoride prevents cavities, then not using fluoride causes cavities.

If video games cause strokes, then not playing may prevent strokes. 

However, in the world of science, a hypothesis that we cannot demonstrate to be wrong is useless.

What Is a Theory?

three clear beakers placed on tabletop
Image by Hans Reniers via Unsplash

“Theoretically” is the adverb form of the noun “theory,” and a solid definition of “theory” will help you to better grasp what it is to speak “theoretically.”

According to the Cambridge Dictionary, a theory is a formal statement of rules that apply to a subject of study. It is an overarching idea to explain particular facts or events. In general terms, a theory is a collection of facts leading to an explanatory principle.

The explanatory principle may still prove to be wrong, but a theory carries more weight than a hypothesis since it involves experimentation.

An authority must test every scientific theory and vet it thoroughly for the scientific community to accept it. Ultimately, all scientific theories begin as untested hypotheses, and the more testing it undergoes, the greater authority it gains.

Dan’s hypothesis that there is more than one universe is now a proven theory.

My hypothesis that the North Star is the brightest is now a general theory in Astronomy.

We find theories in various fields of study, such as economics, education, and science. A scientific theory is an authenticated explanation of the natural world in biology, astronomy, physics, and chemistry.

Although we accept these to be proven theories, they are, in fact, fluid to some degree, as subsequent data may require theorists to modify the theory.

AstronomyThe Big Bang Theory, Newton’s Theory of Gravitation
BiologyTheory of Evolution (Darwin), Cell Theory, Germ Theory of Disease
ChemistryAtomic Theory, Kinetic Theory of Gases
PhysicsGeneral Relativity, Special Relativity, Theory of Relativity, Quantum Field Theory
SociologyFunctionalist Theory, Symbolic Interaction Theory

In our everyday lives, we tend to use the term theory haphazardly. We use it to indicate things we know to be proven (scientific and objective), such as the Earth is round and things we don’t know to be true (subjective), such as the existence of ghosts.

A more colloquial definition of a theory is nothing more than doubtful knowledge gained through speculation (an educated guess). Many often use it to refer to a hunch, which tends to make scientists’ blood boil.

Scientific Examples
(Based in Fact)
Subjective Examples
(Based on personal beliefs)
Newton’s Theory of Gravitation is indisputable.The teacher’s theory was that Billy started the fight, but there were no witnesses.
The ancient Greeks were the first to propose the theory that the Earth is round.I have a theory that I’ll win the lottery even though the odds are against it.
Hubble’s theory, The Big Bang Theory, is one of the various theories explaining how the universe came into being.It is my theory that my next-door neighbor stole my car.

“In Theory”

As humans, we love to say the idiom (phrase) “in theory,” but what does this phrase mean (source)?

According to the Farlex Idioms and Slang Dictionary, “in theory” means, hypothetically, a possibility in contrast to “in reality” (a fact) or “in practice” (a fact).

When we say “in theory,” the intention is to describe something that should happen or is a possibility. It carries with it the connotation that, as a fact, it may never happen. Therefore, in this context, “in theory” means we believe something is true, but it still may not be valid.

To clarify the meaning of theory further, we must look at what context we use the word. For instance, a scientist uses “in theory” to mean something scrutinized through the scientific process, which passes all tests to become a reasonable explanation (source).

We also use the word to explain something we believe in but do not have facts to back us up.

In theory, if you take your medicine every day, you will once again be healthy.

In theory, if you eat carrots, you will have 20/20 vision.

John’s theory is that the neighbor’s dog dug the hole in his backyard. 

Now let’s review the adverb form “theoretically.”


black framed eyeglasses
Image by Jamie Street via Unsplash

The word “theory” is a noun, whereas “theoretically” is an adverb describing something done in a theoretical way. “Theoretical” is the adjective form describing something based on a theory, an idea, or possibilities as opposed to having practical experience with something. It’s more conceptual than tangible. 

Two distinct types of research where scientists must conduct their work theoretically include basic or applied research. Basic research involves a scientist’s drive to further scientific knowledge through investigation and the scientific method.

Her ideas about DNA are theoretically and empirically challenging.

Science journals focus on theoretically sound applied research.

Applied research investigates problems and looks for practical solutions related to our modern world, often dealing with the economy, goods, and services. 

Theoretically, we can find solutions to improve energy efficiency.

It is theoretically possible that one day we will cure every disease. 

In summary, when you speak hypothetically, you use the following format” “If A is true, what will it mean for B?” In the world of science, when one speaks theoretically, the intention is to inform others about a proven set of facts solely for the sake of knowledge. 

It’s interesting to note that many scientists believe it’s time to shift away from basic research solely to gain knowledge and instead toward applied science. Such scientists believe this to be a necessary shift as the world’s problems are growing due to pollution, depletion of our natural resources, and the rapid growth of the world’s population (source).

Speaking Hypothetically or Theoretically

We have discussed the subtle differences between hypothetically speaking and theoretically speaking and teased out the specific definitions. It is often difficult for us to discern the correct term to use, especially when in conversation with others. Therefore, a short review will help cement the differences in your mind.

When we speak hypothetically, we make assumptions that are untested. Generally, you use “hypothetically speaking” as a starting point to an argument. In terms of science, a scientist speaks hypothetically to propose a hypothesis, the first step in the scientific method.

In contrast, when we use “theoretically speaking,” it is always about something that is possible based on certain accepted principles established through scientific research.

In the following chart, you will find examples of hypothetically and theoretically speaking as we use each in both science and everyday conversation.

Hypothetically SpeakingTheoretically Speaking
Basic DefinitionMaking an untested assumption.Making an assumption based on larger, accepted principles.
Everyday UseHypothetically speaking, if fairies are real, what will happen if you catch one?Theoretically speaking, the building will withstand an earthquake with a magnitude of six on the Richter Scale.
Scientific UseHypothetically speaking, it’s a possibility Pluto may regain planet status.Theoretically speaking, this summer will be hotter than last year due to global warming.

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If you enjoy teasing out the subtle differences in like phrases, you may enjoy the following articles: complement vs. supplement and pronunciation vs. enunciation.

Final Thoughts

Hypothetically speaking, after reading this article, you will have no trouble using the phrase. However, theoretically speaking, you, by reading this article, have enough information to discern which phrase to use.

We use hypothetically or theoretically speaking to describe specific assumptions or larger principles. In science, it is crucial to know which term to use. Remember, a hypothesis is untested, while a theory is a formal statement of principles and rules based on experimentation.

One can use either phrase in everyday situations; however, if you happen to find yourself in a lab, knowing the difference between the two phrases may just make or break your career in the sciences.