IB Physics key terms 2026: The essential vocabulary every student must know
IB Physics key terms are the precise scientific words and definitions students need to communicate physical ideas clearly and meet mark scheme expectations. Essential vocabulary spans mechanics, fields, waves, electricity and magnetism, and nuclear and quantum physics, with many definitions requiring specific scientific wording rather than everyday language. Using accurate terminology is especially important in Define, Describe, and Explain questions, where imprecise phrasing can cost marks even when the underlying concept is understood.
This guide explains the most important IB Physics key terms, their meanings, and how students can learn and apply them effectively in exams.
- Key mechanics and motion terms in IB Physics explained
- Key electricity and magnetism terms in IB Physics explained
- Key waves and optics terms in IB Physics explained
- Key nuclear and quantum physics terms in IB Physics explained
- How precise use of key terms earns marks in IB Physics exams
- How to build and revise your IB Physics key term vocabulary
- Frequently asked questions
Key mechanics and motion terms in IB Physics explained
Mechanics forms the backbone of the IB Physics [1] curriculum under Theme A: Space, Time, and Motion. A common mistake we see at Times Edu is students using everyday language when scientific definitions are required, and this costs marks on Paper 2 consistently.
Below are the most critical mechanics terms IB Physics students must be able to define with precision:
| Term | Precise IB definition | Common student error |
|---|---|---|
| Displacement | Linear distance and direction from a fixed reference point (vector) | Writing “distance” instead of “distance and direction” |
| Velocity | Rate of change of displacement with respect to time (vector) | Confusing with speed, which is scalar |
| Acceleration | Rate of change of velocity with respect to time (vector) | Saying “change in speed” rather than “change in velocity” |
| Terminal speed | Constant speed reached when gravitational force exactly balances drag force | Failing to state that net force equals zero |
| Impulse | Product of net force and the time interval of its action, equal to change in momentum | Omitting the phrase “net force” or “change in momentum” |
One critical detail often overlooked is the scalar versus vector distinction. The IB mark scheme will not award a definition mark for “velocity” if you describe it simply as “how fast something moves.” You must state both the rate of change of displacement and the vector nature of the quantity.
Mass vs weight is another classic trap in this theme. Mass is the measure of the amount of matter in an object, measured in kilograms. Weight is the gravitational force acting on that mass, measured in Newtons. In IB Physics, mass and weight are never interchangeable, and using them incorrectly in an explanation will cost you the definition mark every time.
>>> Read more: IB Physics high yield topics 2026: Where to focus your revision for maximum marks
Key electricity and magnetism terms in IB Physics explained
Electricity and magnetism terms in IB Physics appear across both Theme D (Fields and Induction) and the broader electromagnetism topics. Students who struggle here often do so because they carry over informal definitions from IGCSE or other curricula.
The concept of electric field strength is a good example. A common mistake we see is students defining it as “the force in a region around a charge.” This is too vague for the IB mark scheme. The correct definition is: The force per unit positive test charge placed at a point in the field. Every word in that definition carries weight.
| Term | Precise IB definition |
|---|---|
| Electric field strength | Force per unit positive test charge at a point in the field (vector) |
| Gravitational field strength | Force per unit mass at a point in the field (vector) |
| Electric potential | Work done per unit positive test charge in bringing a small positive charge from infinity to that point |
| Gravitational potential | Work done per unit mass in bringing a small test mass from infinity to that point |
| Magnetic flux | Total magnetic field passing through a given surface area, measured in Webers |
| Electromagnetic induction | Generation of an EMF across a conductor due to a changing magnetic flux linking the circuit |
Notice the structural parallel between gravitational and electric field quantities. This is intentional in the IB curriculum design, and recognizing this pattern helps students learn both sets of definitions together rather than as isolated facts.
Drawing on years of experience at Times Edu, we find that students who understand the conceptual symmetry between gravitational and electric field terms learn both topics significantly faster. When you see “per unit mass” for gravity and “per unit positive test charge” for electricity, you are looking at the same mathematical structure applied to two different fields.
>>> Read more: IB Physics HL vs SL 2026: How to choose the right level for you
Key waves and optics terms in IB Physics explained
Waves and optics terminology in IB Physics requires both definitional precision and the ability to distinguish between concepts that sound similar but carry distinct meanings.
The most fundamental distinction is transverse vs longitudinal waves. A transverse wave is one in which the oscillation of particles is perpendicular to the direction of wave propagation. A longitudinal wave is one in which the particle oscillation is parallel to the direction of wave travel. Light is transverse. Sound is longitudinal. In an IB explanation question, you must use the words “perpendicular” or “parallel” explicitly; describing it as “up and down” versus “back and forth” will not earn the mark.
| Term | Precise IB definition |
|---|---|
| Simple Harmonic Motion (SHM) | Periodic motion where acceleration is directly proportional to displacement from equilibrium and acts in the opposite direction |
| Coherent waves | Waves with the same frequency, wavelength, and a constant phase difference |
| Superposition | When two or more waves meet, the resultant displacement equals the vector sum of individual displacements |
| Standing wave | Formed by superposition of two identical waves traveling in opposite directions; has fixed nodes and antinodes |
| Node | A point on a standing wave where displacement is always zero |
| Antinode | A point on a standing wave where displacement is at maximum amplitude |
One critical detail often overlooked is the definition of coherent waves. Many students write that coherent waves have “the same frequency,” which is necessary but not sufficient. The IB mark scheme also requires a constant phase relationship. Without that phrase, the definition is incomplete.
For SHM, the examiner expects you to reference both the proportionality between acceleration and displacement and the opposite direction of that acceleration. The mathematical representation, where acceleration is proportional to negative displacement, must be either stated in words or shown as the equation a ∝ -x.
>>> Read more: IB Physics mark scheme 2026: How to read and use it to raise your grade
Key nuclear and quantum physics terms in IB Physics explained
Nuclear and quantum terms in IB Physics appear in Theme E and often represent the area where students lose the most marks on written questions. The definitions here are highly specific, and paraphrasing them even slightly can result in a lost mark.
In our experience working with international students, the most frequently mishandled term in this section is binding energy. Students often say it is “the energy holding the nucleus together,” which sounds correct but misses the precise IB definition. Binding energy is the minimum energy required to completely separate all the nucleons of a nucleus into individual, isolated components. The word “minimum” and the phrase “individual components” (or equivalent) are critical.
| Term | Precise IB definition |
|---|---|
| Binding energy | Minimum energy required to separate all nucleons of a nucleus into individual isolated nucleons |
| Half-life | Time taken for half the radioactive nuclei in a sample to decay |
| Work function | Minimum energy required to liberate an electron from the surface of a specific metal |
| Photoelectric effect | Emission of electrons from a metal surface when electromagnetic radiation above the threshold frequency is incident on it |
| Quantum tunneling (HL) | Process where a particle passes through a potential energy barrier that it classically does not have enough kinetic energy to overcome |
Half-life is another term where precision matters enormously. The definition must state “half of the radioactive nuclei” not “half of the atoms” or “half of the sample.” Radioactive decay refers to unstable nuclei specifically, and using imprecise language will not satisfy the mark scheme.
For quantum tunneling, which is an HL-only concept, the key phrase the examiner looks for is “potential energy barrier” combined with the idea that the particle classically lacks sufficient energy to cross it. Simply saying “a particle passes through a barrier” earns no marks.
>>> Read more: IB Physics SL exam tips 2026: How to maximise your score across both main papers
How precise use of key terms earns marks in IB Physics exams
The IB Physics mark scheme is structured around command terms, and understanding how they interact with precise IB Physics vocabulary is what separates a grade 5 student from a grade 7 student on written papers.
Here are the most important command terms and what they demand from your answer:
| Command term | What the examiner expects |
|---|---|
| State | A brief, direct answer with no explanation required |
| Define | A complete, precise definition using accepted scientific language |
| Describe | A detailed account of characteristics, appearance, or sequence of events |
| Explain | A cause-and-effect chain that shows why or how something occurs |
| Derive | A full algebraic sequence beginning from a formula in the data booklet |
| Outline | A brief summary that captures the key points without full elaboration |
A common mistake we see is students treating “describe” and “explain” as interchangeable. They are not. If a question asks you to “explain why a ball reaches terminal speed,” you must include the cause-and-effect logic: As speed increases, drag force increases, until drag equals gravitational force, at which point net force is zero and acceleration becomes zero, resulting in constant velocity. Simply saying “the forces are balanced” is a description of the end state, not an explanation of the process.
Drawing on years of experience at Times Edu, we advise students to read the command term before they write a single word of their answer. This single habit can recover two to four marks per exam paper.
>>> Read more: IB Physics how to get a 7 2026: The complete strategy guide
How to build and revise your IB Physics key term vocabulary
Knowing the definitions is only useful if you can recall and deploy them accurately under exam conditions. The following approach is what we recommend to students preparing for IB Physics Paper 2 at Times Edu.
Step 1: Create a living glossary. As you study each theme, write the term, the IB-approved definition, and a note of the specific word or phrase the mark scheme prioritizes. Do not copy definitions verbatim from a textbook; rewrite them in your own words and then compare against the official definition.
Step 2: Use active recall, not passive reading. Cover the definition column of your glossary and attempt to write the full definition from memory. Check your answer against the precise wording. This process is more effective than re-reading notes.
Step 3: Practice with past paper mark schemes. After answering a “define” or “explain” question, compare your response word-for-word against the mark scheme. Identify which specific phrases you missed and add those to your glossary.
Step 4: Group related terms together. Revise gravitational and electric potential together. Revise nodes and antinodes together. Revise precision and accuracy together. The IB curriculum is designed so that parallel concepts appear in multiple themes, and revising them in pairs reinforces understanding.
Step 5: Revisit high-frequency terms weekly. Terms like displacement, velocity, electric field strength, and binding energy appear across multiple paper sections. These deserve regular review rather than single-session learning.
One critical detail often overlooked is the difference between precision and accuracy in the context of IB Physics practical work. Precision refers to how close repeated measurements are to each other, indicated by small uncertainty values. Accuracy refers to how close the measured value is to the accepted true value. Many students use these interchangeably in their Internal Assessment reports and lose criterion marks as a result.
>>> Read more: IB Physics past papers 2026: The complete guide to finding and using them effectively
Frequently asked questions
What physics vocabulary must you know for IB Physics?
Why does using precise terminology matter in IB Physics written answers?
What are the most commonly misused terms in IB Physics?
What is the difference between mass and weight in IB Physics?
How do you define electric field strength correctly in IB Physics?
What is the difference between transverse and longitudinal waves in IB Physics?
How do IB Physics key terms differ from IGCSE Physics terminology?
Conclusion
At Times Edu, we work with IB Physics students from the beginning of their two-year program to ensure that precise terminology becomes second nature, not an afterthought during revision. If you want a personalized assessment of where your IB Physics vocabulary currently stands and a structured plan to close the gaps before your exams, our academic consultants are available for one-on-one sessions designed specifically for international curriculum students. Reaching grade 7 in IB Physics is achievable, and the language you use in written answers is one of the most controllable factors in getting there.
