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Command words are the instruction verbs at the start of a question — state, describe, explain, compare, evaluate and so on. They tell you exactly what kind of answer the examiner wants and how much to write. Misreading or ignoring the command word is one of the most common reasons students lose marks in GCSE Biology: two candidates can know identical biology, but the one who responds correctly to the command word scores higher.
By the end of this lesson you should know every command word OCR uses, be able to recognise what each demands, and avoid the two classic traps — describe versus explain and compare versus contrast.
| Command word | What it asks for | What to write |
|---|---|---|
| State / Name / Give / Identify | A short fact, no explanation | A word or short phrase |
| Define | The precise scientific meaning of a term | A concise, exact definition |
| Describe | What happens or what the data shows | An ordered account of features, steps or trends — no reasons |
| Explain | What happens and why | A linked chain of reasoning with "because"/"so" |
| Compare | Similarities and differences | Explicit point-by-point comparisons |
| Suggest | Apply knowledge to an unfamiliar context | A reasonable, scientific response using the given information |
| Calculate | Work out a numerical value | Formula, substitution, working and answer with units |
| Determine | Use given data or a calculation to find a value | Working that leads to the value the data imply |
| Estimate | A rough but reasoned value | A sensible figure with brief justification |
| Evaluate | Strengths and weaknesses, then a conclusion | A balanced judgement supported by evidence |
| Justify | Reasons supporting a decision or conclusion | The decision plus the evidence/reasoning for it |
The sections below give a precise definition and a short worked example answer for each of the most important ones.
Meaning: write a short, factual answer. No explanation is needed. Usually 1 mark.
Exam Tip: If the word is state or name, keep it to a word or short phrase. A long explanation wastes time and can introduce an error that contradicts your correct answer.
Meaning: give the exact scientific meaning of a term. Usually 1–2 marks.
Exam Tip: OCR definitions are marked on specific key words. Forgetting "partially permeable membrane" in the osmosis definition, or "fertile" in the species definition, can cost you the mark even though the rest is right.
Meaning: say what happens, or what the data shows — an ordered account of the main features, steps or patterns. Do not give reasons. Usually 2–4 marks.
Exam Tip: When describing data, quote figures. "The rate increases" is weak; "the rate increases from 5 cm³/min at 20 °C to 18 cm³/min at 40 °C" is a describe answer that scores.
Meaning: say what happens and why — give reasons or mechanisms, not just an account. Usually 2–6 marks.
Exam Tip: The single most common command-word error is describing when asked to explain. Make sure every explain answer contains a reason — signalled by "because", "this means that" or "so".
Meaning: give similarities AND differences between two or more things, using explicit linking language. Usually 2–4 marks.
A genuine comparison links the two things in each point ("A does X, whereas B does Y"). Listing features of one thing, then separately listing features of the other, is weaker and often loses marks because the examiner has to make the comparison for you.
Exam Tip: Compare is not the same as contrast. Contrast asks for differences only; compare asks for both similarities and differences. If you only give differences to a "compare" question, you cap your marks. Use the words both, whereas, however, similarly, unlike to make each comparison explicit.
Meaning: apply your knowledge to a new or unfamiliar situation. There may be more than one acceptable answer. Usually 1–3 marks.
Exam Tip: Suggest signals AO2 — you are not expected to have seen the exact scenario. Stay calm, use the details in the question, and apply what you know.
Meaning: work out a value using numbers. You must show working. Usually 1–3 marks.
Determine is similar but often expects you to extract the data you need from a graph or table first, then calculate.
Exam Tip: Even a wrong final answer can earn method marks if your formula and substitution are shown. Always write the formula, substitute, and give the answer with correct units (magnification is the exception — it has no units).
Meaning: weigh advantages and disadvantages (or strengths and weaknesses), then reach a supported conclusion. Usually 4–6 marks.
Exam Tip: The conclusion is essential — the top level of the mark scheme requires a supported judgement. An evaluate answer that lists pros and cons but never concludes cannot reach full marks.
Meaning: give the reasons that support a decision or conclusion. Usually 2–4 marks.
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