Cambridge IGCSE mark scheme abbreviations: a teacher's guide
Cambridge IGCSE mark schemes use a short code to tell markers when to give a mark, when a mark depends on another, and which alternative answers to accept. The most important ones are M (method), A (accuracy, depends on the method mark), B (independent mark), ft (follow through), oe (or equivalent), cao (correct answer only), isw (ignore subsequent working) and, in science, owtte (or words to that effect), ora (or reverse argument) and ecf (error carried forward).
This guide is for teachers marking mocks and past papers. Each abbreviation has a plain-English meaning and a short worked example. The example answers are our own illustrations, not reproduced Cambridge questions.
Why do the abbreviations differ between subjects?
Every Cambridge mark scheme opens with the same Generic Marking Principles. The abbreviations underneath them vary by subject, and sometimes by paper. The June 2024 Biology (0610) and Physics (0625) Paper 4 mark schemes each print their own key. The Chemistry (0620) mark scheme for the same series has no key at all and relies on wording such as "ORA" and "not".
Always read the key on the first pages of the specific mark scheme you are using. The tables below cover the conventions you will meet most often.
The six Generic Marking Principles, in plain English
These sit at the top of every Cambridge IGCSE mark scheme and apply to every question.
- Mark to the mark scheme and the standard. Award marks in line with the mark scheme content and the standard set at standardisation.
- Whole marks only. Never award half marks.
- Mark positively. Credit valid answers, even ones beyond the syllabus. Do not deduct marks for errors or omissions. Spelling and grammar only matter when the question assesses them, or when meaning becomes unclear.
- Apply rules consistently, for example when a candidate ignores an instruction.
- Use the full mark range. Don't hold back full marks from an answer that earns them.
- Ignore grade thresholds while marking. Award marks against the mark scheme only, not against what you think a grade A answer "should" look like.
Principle 6 is the one teachers most often break during mocks. If you find yourself thinking "this feels like a B", stop and go back to the marking points.
Maths abbreviations (Cambridge IGCSE Mathematics 0580)
| Code | Stands for | What it means for you |
|---|---|---|
| M | Method mark | Awarded for a correct method, even if the arithmetic then goes wrong. |
| A | Accuracy mark | Awarded for a correct answer or step. It depends on the related M mark being earned or clearly implied. |
| B | Independent mark | Awarded for a correct result or statement, regardless of method. |
| dep | Dependent | This mark can only be awarded if a named earlier mark was awarded. |
| FT / ft | Follow through | Credit correct work that follows on from the candidate's own earlier wrong answer. |
| oe | Or equivalent | Accept any mathematically equivalent form, e.g. 0.5, 1/2, 2/4. |
| cao | Correct answer only | Only the exact answer printed earns the mark. Equivalents and follow-through are not accepted. |
| isw | Ignore subsequent working | Once the correct answer is seen, ignore later working that spoils it. |
| SC | Special case | A specific mark for a common partial or alternative answer that doesn't fit the main scheme. |
| nfww | Not from wrong working | A correct answer reached through incorrect working does not earn the mark. |
| soi | Seen or implied | The step need not be written if later work shows it was done. |
| [ ] | Square brackets | Not required, but must be correct if the candidate includes it. |
| awrt | Answer which rounds to | Accept any answer that rounds to the value given. It appears in some 0580 mark schemes (e.g. the 2025 specimen) but not all. |
Worked example: M1 A1 with follow through
Illustrative question: A jacket costs $80. It is reduced by 15%. Find the sale price. [2]
Mark scheme style: M1 for 80 × 0.85 oe then A1 68 cao
| Student answer | Marks | Why |
|---|---|---|
| 80 × 0.85 = 68 | 2 | Method and answer correct. |
| 80 × 0.85 = 66 | 1 | M1 for the method. A1 lost because the arithmetic is wrong. |
| 80 − 12 = 68 | 2 | Equivalent method (oe). The 12 implies 15% of 80 was found. |
| 68 with no working | 2 | A correct answer with no working normally earns full marks unless the question says "show your working". Check the scheme's own guidance. |
| 80 × 0.15 = 12 | 0 or 1 | Depends on whether the scheme credits finding 15% as a method step. Read the specific scheme. |
What the maths-specific rules add
Recent 0580 mark schemes add maths-specific principles on top of the generic ones:
- Any correct method earns credit, even if it isn't the one shown in the scheme. A scale drawing doesn't count where a calculation is required.
- Marks once gained are not lost. If the correct answer appears and the candidate then makes an error, apply isw.
- Misreads lose only one mark. If a candidate copies a number wrongly and then works correctly, deduct one A or B mark rather than everything.
- Recovery within working is allowed. A candidate can correct an error later in the same working.
Science abbreviations (Biology 0610, Chemistry 0620, Physics 0625)
| Code | Stands for | What it means for you |
|---|---|---|
| ; | Separator | Separates individual marking points. |
| / | Alternatives | Any one of the answers separated by / earns the mark. |
| A | Accept | An acceptable alternative wording. |
| R | Reject | This answer does not earn the mark, even if it seems close. |
| I | Ignore | Neither credit nor penalise this. Treat it as if it wasn't written. |
| owtte / AW | Or words to that effect / alternative wording | Credit the idea even if the wording differs. |
| ora | Or reverse argument | Accept the same point made from the other direction, e.g. "B is smaller than A" for "A is bigger than B". |
| ecf | Error carried forward | Credit a correct method using a value the candidate got wrong earlier. |
| AVP | Any valid point | Credit other correct points not listed (Biology). |
| Underline | Essential word | The underlined word, or a clear equivalent, must appear. |
| ( ) | Brackets | Not required, but gives context for the marking point. |
| max n | Maximum | No more than n marks from this list, however many points are made. |
| C | Compensatory mark | Awarded for a correct final answer, which compensates for missing method marks (Physics). |
| CON | Contradiction | A contradictory statement cancels the mark (Physics). |
Science-specific rules that catch teachers out
These come from the Science-Specific Marking Principles printed in recent IGCSE science mark schemes:
- The list rule. If the question asks for two answers and the student writes four, mark only the first two. Wrong answers count towards the two; answers marked "ignore" do not.
- Contradictions. If a student writes a correct and an incorrect statement together, you don't pick the correct one. The mark is lost.
- Units. A missing or wrong unit normally costs the final mark in calculations.
- Spelling. Spelling need not be perfect. But words that could be confused with another syllabus term (ethane/ethene, meiosis/mitosis) must be clearly distinguishable.
- Equations. Multiples of the coefficients in balanced equations are acceptable. State symbols are ignored unless the question asks for them.
Worked example: the list rule
Illustrative question: State two factors that increase the rate of photosynthesis. [2]
Student answer: "Light intensity, oxygen concentration, temperature."
Mark: 1. Light intensity is credited. Oxygen concentration is wrong and counts as the second answer. Temperature is the third answer, so it is not marked, even though it is correct.
Do Edexcel International GCSE mark schemes use the same codes?
Mostly, but not exactly. Pearson Edexcel International GCSE Maths (4MA1) uses M1, A1, B1, cao, ft, isw, SC, oe, dep, awrt, and eeoo ("each error or omission"). See our Edexcel International GCSE mark scheme guide for the differences.
How AI marking tools handle these conventions
A marking tool is only as good as its grip on these rules. When you test any AI marking tool, including ours, check three things:
- Does it apply dependency? It should never award an A mark when the M mark wasn't earned or implied.
- Does it apply the list rule in science, rather than crediting the best answers?
- Does it show you the marking point behind each mark, so you and your students can see why it was given?
The Learning Mate marks handwritten or typed scripts against the mark scheme you provide, question by question and part by part. You see the reasoning for every mark, and you can change any mark before you publish results. Try it on one script at thelearningmate.com/trial. No account is needed.
FAQ
What does owtte mean in a mark scheme?
It means "or words to that effect". Credit the student's answer if it expresses the same idea as the mark scheme, even in different words.
What is the difference between M1 and A1?
M1 is a method mark for a correct approach. A1 is an accuracy mark for a correct answer or value, and it normally depends on the related method mark being earned.
What does B1 mean in IGCSE maths mark schemes?
B1 is an independent mark. It is awarded for a correct answer or statement on its own, without depending on any method mark.
What does ecf mean?
"Error carried forward." If a student gets an early value wrong but uses it correctly in later steps, they can still earn the later marks.
Can I give half marks when marking IGCSE papers?
No. Cambridge's Generic Marking Principles say marks are awarded in whole numbers only.
What does ora mean in Cambridge mark schemes?
"Or reverse argument." Accept the same point expressed the other way round, for example "the rate decreases as temperature falls" for "the rate increases as temperature rises".
Sources
- Cambridge IGCSE Mathematics 0580, June 2024 Paper 41 mark scheme and 2025 specimen Paper 2 mark scheme: cambridgeinternational.org
- Cambridge IGCSE Biology 0610, Chemistry 0620 and Physics 0625, June 2024 Paper 41 mark schemes, via each syllabus's past papers page on cambridgeinternational.org
- Pearson Edexcel International GCSE Mathematics A 4MA1, Summer 2025 Paper 1H mark scheme: qualifications.pearson.com