IB Physics command terms tell you what kind of answer to give and how much depth it needs. A student may understand the physics but still lose marks by explaining when asked to state, describing when asked to explain, or giving an unsupported opinion when asked to evaluate.
For the Physics course with first assessment in 2025, the official guide groups its listed command terms by assessment objective. However, the guide also warns that other wording may direct students to present an answer in a particular way. You therefore need to understand both the current list and broader instructions such as evaluate or justify, especially when reviewing older questions or completing scientific work.
Why IB Physics command terms matter
A command term is the instruction at the beginning of a question, such as state, calculate, explain, or suggest. According to the IB's assessment guidance, command terms indicate the type and depth of response expected.
They affect three important decisions:
- Content: facts, calculations, reasoning, evidence, or judgment
- Depth: a brief answer, detailed account, or developed argument
- Presentation: words, algebra, a graph, a diagram, or a combination
Command terms do not provide an exact word count. The number of marks and the context still matter. A two-mark explanation normally needs two linked pieces of creditworthy reasoning, while a six-mark discussion requires a substantially broader response.
The current Physics assessment objectives progress from demonstrating knowledge to applying knowledge and then analysing, evaluating, and synthesizing information. This is why apparently similar questions can require very different responses.
The most important command terms at a glance
The following table combines the command terms listed in the current Physics guide with practical exam interpretation.
| Command term | What it requires | Typical response depth | Physics example |
|---|---|---|---|
| State | A specific name, value, or brief answer without explanation or calculation | One phrase or sentence | “State the SI unit of force.” Answer: newton, N. |
| Outline | A brief account or summary | Main points only | Summarize how an alternating current is induced. |
| Describe | A detailed account of what happens | Several precise observations or stages | Describe the motion shown by a velocity-time graph. |
| Explain | A detailed account including reasons or causes | Linked statements showing why or how | Explain why gas pressure rises when temperature increases at constant volume. |
| Calculate | A numerical answer with relevant stages of working | Equation, substitution, result, unit | Calculate the kinetic energy of an object. |
| Estimate | An approximate numerical value | Sensible assumptions and approximate working | Estimate the power output of a student climbing stairs. |
| Analyse | Break information down to reveal important elements or structure | Patterns, relationships, and implications | Analyse a graph to identify the mathematical relationship between variables. |
| Deduce | Reach a conclusion from information supplied | Evidence followed by conclusion | Deduce the direction of the magnetic force from the diagram. |
| Determine | Obtain the only possible answer | Sufficient reasoning or calculation | Determine the resistance from the graph's gradient. |
| Discuss | Give a balanced review of relevant factors or hypotheses | Multiple sides, evidence, and conclusion | Discuss whether the data support a proposed model. |
| Predict | Give an expected result | Clear expected outcome, with reasoning if the question requests it | Predict how the diffraction pattern changes when wavelength increases. |
State, outline, describe, and explain
These four terms form a useful depth ladder, but they are not interchangeable.
State
State requires only the answer. If asked to state the principle of conservation of momentum, write a precise statement such as: “The total momentum of an isolated system remains constant.” Do not add a paragraph unless another part of the question requests justification.
Overwriting wastes time and can introduce contradictions. A state question may still require a unit, direction, or sign if these are essential to the requested quantity.
Outline
Outline asks for a brief summary containing the main stages or features. For example, to outline energy changes in a falling object with air resistance, you might state that gravitational potential energy decreases while kinetic and thermal energy increase.
This is more developed than stating one fact but less detailed than describing every stage. Focus on the skeleton of the process.
Describe
Describe means give a detailed account of what happens. In a graph question, report the trend, relevant regions, turning points, and quantitative features where available.
For example: “From 0 to 4 seconds, velocity increases linearly from 0 to 12 m s⁻¹, so acceleration is constant.” This describes the graph accurately without necessarily explaining the physical cause.
Explain
Explain adds why or how. A reliable structure is claim + physics principle + causal link.
Consider the question: “Explain why the pressure of a fixed mass of gas increases when it is heated at constant volume.” A strong answer states that heating increases the particles' mean kinetic energy, so they collide with the walls more frequently and with a greater change of momentum. The resulting greater rate of momentum transfer produces a larger force per unit area, so pressure increases.
Saying only “the particles move faster” is relevant but incomplete because it does not finish the causal chain leading to pressure.
Numerical and mathematical command terms
Calculate, estimate, and determine
For calculate, show the relevant stages even if you can obtain the result mentally. Write the equation, substitute values consistently, and include the final unit. Clear working can earn method credit when the final number is wrong.
An estimate is not a guess. State sensible approximations, use an appropriate model, and give a result with realistic precision. For instance, estimating a person's gravitational potential energy gain requires reasonable values for mass, vertical height, and gravitational field strength.
Determine means obtain the only possible answer from the information available. The method could involve calculation, graph interpretation, or logical reasoning, so do not assume that every determine question requires an equation.
Show and show that
Show requires visible mathematical or logical steps. Beginning with the target result and merely asserting that it is correct does not demonstrate anything.
In older materials, show that commonly means obtaining a supplied result without requiring a formal proof. Because the answer is already given, your working is the entire point. Avoid premature rounding, as it may prevent your calculation from matching the stated value.
Sketch and draw
A sketch communicates the general shape and relevant features. Include labelled axes, intercepts, asymptotes, maxima, minima, and direction where appropriate, but exact plotting is not expected.
A draw instruction requires greater accuracy. The current guide specifies a labelled, accurate diagram or graph, with straight edges used for straight lines and diagrams drawn to scale. This distinction matters because a rough curve may satisfy sketch but not draw.
Higher-order command terms
Analyse and deduce
To analyse, break data or a situation into meaningful components and identify relationships. In Physics, this often includes calculating gradients, recognizing proportionality, comparing regions, or connecting uncertainty to the strength of a conclusion.
To deduce, start from the supplied evidence and reach a conclusion. Make the link visible: “The gradient is constant, so acceleration is constant.” A correct conclusion with no connection to the given information may not receive full credit.
Discuss and evaluate
Discuss requires a considered, balanced review. Address relevant arguments, evidence, limitations, or alternative explanations, then reach a supported conclusion rather than presenting disconnected advantages and disadvantages.
Students often encounter evaluate in scientific investigations, teacher-written tasks, and legacy resources. The current Physics guide does not include evaluate in its reduced examination command-term table, although evaluation remains part of Assessment Objective 3 and is central to the scientific investigation criteria. When instructed to evaluate, weigh strengths against limitations using stated or implied criteria, explain their consequences, and make an evidence-based judgment.
For example, evaluating an experiment should go beyond saying that “human error occurred.” Identify a specific limitation, explain its likely effect on measurements or conclusions, assess its importance, and propose a realistic improvement that directly addresses it. The RevisionDojo Physics IA command-term glossary is useful when applying these distinctions to the scientific investigation.
Predict and suggest
A prediction is an expected result based on a model, pattern, or principle. If the question asks only for a prediction, state it directly; if it says “predict and explain,” add the physical reasoning.
Suggest allows more than one plausible answer. Your proposal must still be scientifically credible and relevant to the context. Generic responses such as “measurement error” are weaker than specifying parallax, heat loss, limited instrument resolution, or an uncontrolled variable.
Common mistakes that lose marks
- Describing instead of explaining: reporting that current decreases without explaining the resistance or potential-difference relationship responsible.
- Explaining a state question: spending time on reasoning that was not requested.
- Giving unsupported evaluation: listing “accurate” or “unreliable” without evidence or criteria.
- Hiding calculation stages: providing only a calculator result when working is required.
- Ignoring the object of the command: explaining the theory generally instead of the specific observation in the question.
- Treating marks as a strict sentence count: one sentence can contain several ideas, while several vague sentences may earn no credit.
- Forgetting graph conventions: omitting axis labels, units, key features, or an appropriate line or curve.
The RevisionDojo guide to Physics data analysis provides further practice distinguishing description, calculation, and evaluation in graph-based questions.
How to internalise command terms efficiently
Memorising definitions is a starting point, but it does not automatically produce strong answers. The fastest method is to watch and study many questions being worked through so that you see how the response changes with the command term and mark allocation.
Use this practice cycle:
- Underline the command term and identify the exact object of the question.
- Predict the answer shape before solving: value, causal chain, graph, conclusion, or balanced review.
- Answer under a short time limit.
- Compare your response with a worked solution or marking guidance.
- Label the error: physics knowledge, command-term depth, evidence, calculation method, or presentation.
- Rewrite only the missing part, then attempt a similar question later.
RevisionDojo's IB Physics resource hub supports topic-based practice, while the Physics video library and worked solutions let you observe how individual questions are interpreted and solved. Per-question video solutions are particularly useful because they make the difference between an acceptable response and a fully developed one visible.
Once individual skills are secure, use IB Physics predicted papers or timed mixed sets. Jojo AI can help identify whether an error came from missing physics, insufficient explanation, or failure to follow the command term.
Exam-day decision process
Before writing, ask four questions:
- What action is required? State, calculate, explain, analyse, or another instruction?
- What exactly must I act on? A graph, observation, model, method, or conclusion?
- How much evidence is suggested by the marks?
- What form should the answer take? Words, equations, diagram, or a combination?
Then answer directly. Physics responses do not become stronger merely by becoming longer. They become stronger when each sentence contributes a relevant fact, relationship, reason, calculation, or judgment.
Conclusion
IB Physics command terms control the form and depth of an answer. State is brief, outline summarizes, describe reports what happens, and explain establishes why or how; mathematical and higher-order terms require their own equally distinct response structures.
Learn the definitions, but build fluency through repeated questions and worked examples. RevisionDojo's Physics Questionbank, Jojo AI feedback, and per-question video solutions can help you compare your response with the depth the instruction actually demands.
Sources and referenced URLs
- Official IB Physics subject brief, first assessment 2025
- Official IB Physics curriculum and assessment updates
- Official IB assessment principles and practices
- IB Physics resources on RevisionDojo
- RevisionDojo Physics videos and worked solutions
- RevisionDojo Physics IA command-term glossary
- RevisionDojo guide to IB Physics data analysis
- RevisionDojo Physics predicted paper
