What is the difference between explain and describe in the HSC?

In NESA's glossary, describe asks you to set out the characteristics and features of something. Explain asks you to link cause and effect, make clear how things relate, and say why and/or how. So a describe answer can be a list of features, while an explain answer needs a link between a cause and what follows from it. In the 2024 Biology Marking Guidelines a 3-mark explain question is marked on whether you explain how a campaign will lower disease incidence, with outlining the features of a campaign worth only 2.

Is there a key word for every HSC exam question?

No. NESA says HSC questions will keep using self-explanatory words such as how, why and to what extent, and some verbs that papers use are not defined in the glossary. Plot, draw, show and determine are not among its entries, and the Marking Feedback for mathematics singles out show, solve, evaluate, hence and calculate for that course.

Do key words mean the same thing in every HSC subject?

Mostly, and that is the glossary's stated purpose. NESA also warns against rigid readings and gives evaluate as an example: it asks for a different response in Maths than in History. Check how your subject's Marking Guidelines use the word.

How many marks are key words like identify and outline usually worth?

In the 2024 Biology and Chemistry parts used as examples in this guide, the identify and outline parts were worth 2 marks each and the explain parts ran from 3 to 5. Those are examples, not a rule, because the marks printed beside each part set the depth you need.

Do these figures show how the HSC cohort performed?

No. The averages in the table come from marked attempts by AusGrader users who chose what to practise, and the paper examples come from NESA's own Marking Guidelines. Neither is NESA cohort data.

HSC Command Terms: NESA's Key Words Explained

Q: What does NESA call command terms?

NESA calls them key words. Its page is titled Glossary of key words, and the Marking Feedback for Biology, Chemistry and Physics tells students to know what the key words in a question mean and to work out what the question is asking for. Physics refers to the glossary of key words by name. NESA does not use the terms command word or directive verb in that feedback.

HSC command terms are the verb at the start of an exam question, and NESA calls them key words. Each one tells you what kind of answer earns the marks: identify wants a name, outline a general sketch of the main features, describe the characteristics and features, and explain the cause and effect, the why or the how. NESA publishes a Glossary of key words, and its Marking Guidelines show how a verb turns into marks.

This guide describes the NESA glossary as published in October 2026 and uses the 2024 Biology and Chemistry examinations and Marking Guidelines for its worked examples. It applies to the HSC (Year 12) written exams. The glossary is one list shared by every subject, so check your own subject's Marking Guidelines for how it uses a word. For the exam dates, rules and a full study plan, see how to prepare for HSC exams.

What does NESA call command terms?

NESA's term is key words. The glossary says it exists to help students see that a key word asks for much the same thing in exam questions whatever the subject. Its example is explain, which it says may need you to show a cause and effect, make clear how things relate, or say why and/or how.

NESA's Marking Feedback for the sciences uses the same word. In all six Biology, Chemistry and Physics reports for 2024 and 2025 the General feedback tells students to know what the key words in a question mean and to work out what the question is asking for. The Physics reports go one step further and name the glossary of key words. None of the six uses the phrases command word or directive verb.

The glossary comes with two cautions. NESA says key words are best learned against the questions you are working on, and that you should avoid rigid readings of them. It also says HSC questions will keep using self-explanatory words such as how, why and to what extent, which are not glossary entries.

What does each HSC key word mean?

The glossary is one alphabetical list for all subjects. The tables below put NESA's entries into three groups by what they ask you to do, with each meaning in our own words. The group names are ours, not NESA's.

Key words that ask you to recall, name or give the features

Key word	What NESA asks for
Identify	Pick it out and name it
Recall	Bring back facts, ideas or experiences you have remembered
Define	Say what it means and its essential qualities
Clarify	Make something plain
Classify	Sort things into classes or categories
Extract	Pick out the details that are relevant
Describe	Set out its characteristics and features
Outline	Give a general sketch that shows the main features
Summarise	Give the relevant details briefly
Recount	Tell a sequence of events again
Account	Account for means give the reasons for, or report on. Give an account of means tell the story of a sequence of events or transactions
Construct	Make or build, whether items or arguments

Key words that ask you to relate, explain or work something out

Key word	What NESA asks for
Explain	Link cause and effect, make clear how things relate, and say why and/or how
Analyse	Break it into its parts, show how they relate, and draw out what follows from that
Compare	Set out where things are alike and where they differ
Contrast	Set out where things differ or are opposite
Distinguish	Note what makes one thing different from another
Examine	Look into it closely
Interpret	Work out what it means
Deduce	Reach conclusions
Calculate	Work something out from the facts, figures or information given
Predict	Say what is likely to happen, based on the information you have
Extrapolate	Work out what follows beyond what is known
Apply	Use it in a new or unfamiliar situation
Demonstrate	Show it through an example
Investigate	Plan, look into and reach conclusions about
Synthesise	Combine separate elements into a whole
Propose	Offer an idea, argument, point of view or suggestion for others to consider or act on

Key words that ask you to judge

Key word	What NESA asks for
Assess	Judge its value, quality, outcomes, results or size
Evaluate	Judge it against criteria and work out its value
Appreciate	Judge the value of something
Discuss	Set out the issues and the points for and/or against
Justify	Back up an argument or conclusion
Recommend	Give the reasons for it
Critically analyse	Weigh a range of evidence by interpreting and reasoning, and reach judgements grounded in detailed analysis
Critically evaluate	Evaluate, with added accuracy, knowledge and understanding, logic, questioning, reflection and quality

Some words that papers use are not in the glossary at all. Plot, draw, show and determine do not appear among its entries, and neither does state. A Biology 2024 part reads "Plot the data on the grid provided and include the line of best fit." When a word is undefined, read the question for what is physically asked for and check the Marking Guidelines of past papers in your subject.

How do the Marking Guidelines turn a key word into marks?

The Marking Guidelines show what the glossary leaves open. In the 2024 Biology and Chemistry guidelines, the criteria name the verb of the question ("Explains", "Outlines", "a sound comparison"), and the top mark is given for doing that verb well. In every part of 2 marks or more quoted below, the bottom rung is the same: "Provides some relevant information" for 1 mark.

Outline then explain, 2 and 3 marks (Biology 2024, Question 24)

Part (a) asks students to "Outline the cause of a disease due to environmental exposure" and is worth 2 marks. The top criterion is "Outlines a cause of a disease relating to environmental exposure", and the sample answer is a single sentence naming lung cancer and cigarette smoke.

Part (b) asks students to "Explain how an educational program or campaign can be used to decrease the incidence of a disease caused by environmental exposure" and is worth 3. The criteria step up: 3 marks for "Explains how a program/campaign will help to decrease the incidence of the disease", 2 for "Outlines features of a relevant program/campaign", 1 for "Provides some relevant information". Outlining the features of a campaign earns 2. The third mark is the link from the campaign to fewer cases.

Explain, 4 marks, and identify, 2 marks (Chemistry 2024, Questions 24(b) and 33(a))

Chemistry 24(b) opens "With reference to hydrogen bonding and dispersion forces, explain the trends in the boiling point data" and carries 4 marks. The top band needs two explained trends: boiling point rising with carbon number because of dispersion forces, and the difference between the amine and alcohol series because of hydrogen bonding strength. The lower bands cover explaining only one trend, describing the trends, and making a relevant comparison to a data series, so the marks track how many linked explanations you give. The verb is not the first word of this question, so read the whole sentence for it.

Question 33(a) asks students to "Identify the shape around the central carbon atom in each molecule" for 2 marks. The top criterion is "Identifies correct shape around both central carbon atoms in the reactant and product molecules", and the sample answer is one sentence giving trigonal planar and tetrahedral. Two molecules means two shapes.

The pattern across these examples: the marks do not go up with length. They go up with how fully the answer does what the verb says. An outline stays at the level of features, an explain needs the link, and a compare covers both things.

Which key words carry the marks in Biology, Chemistry and Physics?

On AusGrader, each subject's hardest-topics guide ranks command verbs by how many marks they carry and how students score. The table below pulls out six of the verbs that appear in more than one of those tables. Each figure is for that subject only and should not be read across: explain in Physics is not explain in Biology.

Verb	Biology	Chemistry	Physics
Explain	19.3% of marks, 65.0% average (2,675 attempts)	22.0%, 60.8% (1,927)	19.3%, 57.5% (447)
Identify	2.3%, 67.9% (1,497)	7.3%, 62.5% (993)	1.3%, 66.7% (73)
Justify	7.0%, 69.1% (849)	11.0%, 57.0% (210)	3.0%, 53.6% (76)
Calculate	not listed	19.7%, 63.2% (715)	12.0%, 51.1% (873)
Determine	not listed	6.0%, 65.9% (708)	4.0%, 60.9% (377)
Describe	14.0%, 69.3% (1,467)	not listed	5.0%, 60.0% (170)

"Share of marks" is how much of the 2023 to 2025 papers' marks the verb carries. "Average" is the mean score across marked attempts, and the bracketed number is how many attempts it rests on. "Not listed" means the verb does not appear in that subject's table. The sample is AusGrader users' marked attempts on questions from board external papers (66,575 in Biology, 32,206 in Chemistry and 22,987 in Physics), not the NESA cohort under exam conditions. The averages cover questions mapped to the syllabus from any board's papers, so they are broader than the NESA papers alone.

The full tables, with marks at risk, are on each subject's guide: HSC Biology hardest topics, HSC Chemistry hardest topics and HSC Physics hardest topics. In all three, explain carries the largest share of marks, so it is the key word to get right first.

What do students get wrong with key words?

NESA's Marking Feedback is the board's own account. Our summaries of it:

Stating the effect without the reasoning. The Chemistry 2025 feedback on Question 30(b) asks for clear, logical reasoning that links each factor to its effect, and not a bare statement of the effect. Physics asks students in both years to show clear cause-and-effect relationships in explanations.
Outlining at length or too vaguely. The Physics 2025 feedback on an outline question praises matching the key word outline with concise method descriptions, and asks for outcomes to be stated clearly, so "alpha is stopped, beta passes through" and not "test with paper". It also warns against general statements such as "use a detector".
Missing what a mathematics key word implies. The mathematics reports list show, solve, evaluate, hence and calculate as words whose requirements students need to recognise, and two reports (Extension 1 2025 and Advanced 2024) advise using the marks as a guide to how many steps a solution needs.
Not meeting the requirements of assess. The English Advanced 2024 feedback names understanding the requirements of the key word assess as an area to improve.
Retelling when the question wants analysis. The English Standard 2024 feedback asks for explaining and not recounting events in the text.

What does a weak answer look like against the criteria?

The weak answers below are illustrative, written by us. The right-hand column is what the Marking Guidelines reward, not a full model answer.

Question	An illustrative weak answer	What the guidelines reward
Explain how a campaign can decrease the incidence of a disease (3 marks, Biology 2024)	"A campaign tells people about the disease and its symptoms." Describes a campaign, which at best reaches the outline mark	The link from the campaign to fewer cases, for example that teaching students about UV exposure and skin cancer leads them to wear hats and sunscreen
Compare Process A with DNA replication (3 marks, Biology 2024)	A paragraph on transcription only	What the processes share and how they differ, in the same answer
Explain the trends in the boiling point data (4 marks, Chemistry 2024)	"Boiling points go up as the carbon number goes up." Describes one trend without a reason	An explained trend for dispersion forces and an explained difference between the series for hydrogen bonding

Where do I find the glossary and how should I use it?

NESA publishes the Glossary of key words on its HSC student guide pages. Read it once for the meanings, then check each word against the Marking Guidelines of past papers in your own subject, because the guidelines show what each mark was given for. Past papers and questions with the marking criteria attached are on the HSC Biology, HSC Chemistry and HSC Physics pages, and the HSC past papers guide lists every paper by year. For how the marks you collect become a band, see HSC bands explained. A cross-board comparison of command words is in exam command words explained.

Syllabus and assessment material referenced in this guide is used under licence, © Copyright NSW Education Standards Authority. See our NESA licensing notice. The NSW Education Standards Authority (NESA) does not endorse this product or service. NESA takes no responsibility for any errors in the reproduction of NESA Materials. Any sample examination papers or model answers accompanying the NESA Materials are not part of the NESA Materials and are in no way endorsed or authorised by NESA.