Explain, Describe or Discuss? Physics Exam Command Words

Picture this: two students write almost identical answers to the same question, yet one loses half the marks. The difference often has nothing to do with their understanding of Physics. It comes down to a single word at the start of the question that they either misread or ignored altogether.

Command words are the small instructions tucked into exam questions that tell you exactly what kind of answer is expected. Words like "explain," "describe" and "discuss" might look interchangeable at a glance, but examiners use them with very specific intentions. Getting this distinction right is one of the simplest ways to pick up marks that are otherwise lost to vague or mismatched answers, regardless of how well you actually know the content.

Why Command Words Matter So Much

Physics examiners do not choose their wording carelessly. Every command word is a signal about the type of thinking the question wants from you: whether that is stating facts, showing reasoning, or weighing up different viewpoints. Ignore the signal, and you risk writing a technically correct answer that simply does not address what was asked.

This is especially true at higher levels. Pure O-Level Physics tends to favour clear, direct commands, while A Level H2 Physics, H3 Physics and IB HL Physics often expect longer, more layered responses that combine several command words within a single question. Recognising each one quickly, almost on reflex, frees up valuable time you would otherwise spend rereading the question halfway through your answer.

Describe: State What You Observe

"Describe" asks you to give an account of something without needing to justify why it happens. Think of it as painting a picture in words. You are reporting facts, patterns, or the sequence of events, not explaining the underlying physics.

For example, a question might ask you to describe the motion of a ball thrown vertically upward. A strong response would mention that the ball decelerates on the way up, momentarily stops at the highest point, and accelerates on the way down. There is no need to bring in Newton's laws or discuss forces unless the question specifically asks for that.

Common describe-type prompts include:

• Describe the trend shown in a graph
• Describe how the current changes as resistance increases
• Describe the path of light through a prism

Explain: Justify With Physics Reasoning

"Explain" is where the real physics comes in. This command word wants you to give reasons, causes, or mechanisms behind an observation. It is not enough to state what happens; you need to say why it happens, ideally referencing the correct physics principle or law.

Take the same ball example. If asked to explain the motion instead of describing it, you would need to bring in gravity as the constant downward force acting on the ball, causing it to decelerate as it rises and accelerate as it falls. The addition of cause and effect is what separates a describe answer from an explain answer, and examiners are trained to look for that reasoning specifically.

A helpful way to remember the difference is this simple table:

Command Word	What It Wants	Typical Structure
Describe	What happens	Observation, trend, sequence
Explain	Why it happens	Reason, cause, physics principle
Discuss	Multiple angles	Compare, evaluate, weigh evidence

Discuss: Weigh Up Different Perspectives

"Discuss" is the broadest of the three and appears most often in longer-answer or essay-style questions, particularly at A Level and IB. This command word wants you to consider multiple sides of an issue, compare competing theories, or evaluate the strengths and limitations of a model.

A discuss question might ask you to consider the evidence for and against a particular model of light, or to weigh the advantages and disadvantages of a specific energy source. Here, examiners want breadth of thought. A one-sided answer, however well written, will not score full marks because the question is inherently asking for balance.

How Misreading Command Words Costs Marks

Many students lose marks not because they lack knowledge, but because they answer the wrong type of question. A student who explains when the question only asks them to describe may waste time writing unnecessary detail. Worse, a student who describes when explanation is required will often be marked down for lacking reasoning, even if every fact stated is accurate.

This mismatch becomes particularly costly under time pressure. Recognising command words instantly is part of the broader skill set involved in finishing your science papers on time, since it stops you from second-guessing your approach partway through a response or rewriting an answer that has drifted off track.

Practical Tips for Spotting Command Words Quickly

• Underline the command word the moment you read the question
• Pause and ask yourself what type of answer it demands before writing anything
• If a question uses more than one command word, address each part separately
• Practise past papers with a focus purely on identifying command words, before worrying about content

Over time, this becomes an automatic habit rather than a conscious effort, which is exactly the kind of exam fluency that good JC Physics tuition helps students build through repeated, guided practice.

Ready to Sharpen Your Exam Technique?

Understanding command words is a small but powerful step toward writing sharper, more targeted answers in your Physics papers. If you would like structured guidance on tackling exam questions with precision, from command words to full-length responses, visit Physics.com.sg. Whether you are preparing for O-Levels, IP Physics, A Levels or IB, the right support can help you turn understanding into results.