What Do IB Physics Command Terms Mean and How Are Marks Awarded?

Command terms are the verbs (state, calculate, explain, evaluate) that fix how much detail a question wants. Marks come from a markscheme with specific accepted points — one mark per correct fact, working step or valid reasoning line, not for length. Match your answer's depth to the verb's demand.

State wants a single fact, no justification — one line, no more. Describe wants you to give a detailed account, often several linked points, but still no reasoning why. Explain demands you give reasons or a mechanism — the causal 'because'. Mixing these up is the single most common reason students lose easy marks.

Calculate means show working to reach a numerical answer using a given formula. Determine also wants a numerical or specific answer but often requires you to select the right method or data yourself first. Deduce means use given information to reach a conclusion through logical steps, not a formula plug-in.

Evaluate wants you to weigh strengths and weaknesses of an argument, method or result and reach a supported judgement. Discuss wants a balanced review of an issue from multiple angles, without necessarily concluding. Both need more than one side — a one-sided answer rarely reaches full marks on these command terms.

IB examiners use a markscheme with an ‘own figure rule’ (ecf — error carried forward), so one early slip usually only costs one mark, not the whole calculation. Marks are awarded for specific method steps, correct substitution, correct final value with units, and named physics concepts — not for neat handwriting or extra irrelevant detail.

Because IB Physics mark schemes reward method, not just the final number. If you skip working, an examiner can't award the intermediate marks even when your answer matches the scheme — and some questions specifically flag 'award 0 marks if no working shown' for multi-step calculations.

Yes — unit and significant figure penalties are real and applied consistently across a paper, but typically capped so you lose at most one mark per paper section for this, not per question. Examiners still credit correct method and substitution even if the final unit or rounding slips.

Error carried forward (ecf) means if you make an early mistake but then apply correct physics and method to your own (wrong) number afterwards, you can still earn the later marks. It stops one small slip from destroying an entire multi-part calculation's mark total.

Practise reading the command term first, before you even look at the physics content — decide whether it wants a fact, a calculation, or a reasoned argument. Then check your answer against a real IB markscheme afterwards, not just the final answer key, so you see exactly which phrases earned marks.

The IB publishes a command terms glossary inside the Physics guide itself, alongside subject-specific guidance in the Diploma Programme assessment procedures. Your school should have access to both through the IB's official programme resource centre — ask your Physics teacher if you haven't seen them yet.

No — SL and HL share the exact same command term glossary and marking conventions. The difference isn't the verbs used, it's that HL questions apply those same command terms (explain, derive, evaluate) to more mathematically demanding content, like rotational dynamics or the Additional Higher Level topics.

You can't separate the two on an IB Physics paper — solid content knowledge answered against the wrong command term still loses marks, and a student who understands 'explain' vs 'describe' but lacks content knowledge won't score well either. Both need deliberate practice, ideally together using past paper markschemes.