The 200-word list for a 15-year-old
200 new target words to explore around age 15. A themed word bank, not a required vocabulary total or birthday deadline.
| Number and theme | Words, in sequence |
|---|---|
| 001–020 Reasoning with precision | induction, abduction, syllogism, tautology, fallacy, paradox, dilemma, postulate, axiom, soundness, entailment, warrant, necessity, sufficiency, causation, confounder, counterexample, falsifiability, parsimonious, equivocation |
| 021–040 Law and justice | statute, ordinance, precedent, litigation, plaintiff, defendant, prosecution, defence, ruling, acquittal, tribunal, appellate, injunction, restitution, compensation, negligence, tort, culpability, jurisprudence, adjudication |
| 041–060 Economics and incentives | utility, inelastic, externality, subsidy, taxation, fiscal, monetary, liquidity, expenditure, depreciation, aggregate, marginal, unemployment, disequilibrium, specialisation, comparative, profitability, redistribution, austerity, stimulus |
| 061–080 Psychology and behaviour | cognition, perception, arousal, motivation, temperament, disposition, attachment, conditioning, reinforcement, habituation, inhibition, salience, metacognition, volition, introspection, suppression, aversion, gratification, dissonance, heuristic |
| 081–100 Style and rhetoric | rhetoric, diction, prosody, cadence, parallelism, antithesis, juxtaposition, oxymoron, euphemism, understatement, anaphora, allusion, connotation, denotation, sociolect, idiom, colloquialism, jargon, ambiguity, subtext |
| 101–120 Research and evidence | empirical, theoretical, qualitative, quantitative, longitudinal, demographic, experimental, observational, systematic, randomisation, stratification, triangulation, enrolment, sampling, scrutiny, preregistration, methodology, operationalisation, extrapolation, interpolation |
| 121–140 Technology and society | orchestration, augmentation, digitisation, interoperability, scalability, redundancy, modularity, usability, localisation, personalisation, moderation, surveillance, profiling, traceability, observability, auditability, explainability, decentralisation, centralisation, optimisation |
| 141–160 Principles and choices | ethics, morality, autonomy, beneficence, mutuality, rectitude, nonviolence, proportionality, minimisation, stewardship, fraternity, altruism, obligation, entitlement, custodianship, harm, exploitation, assent, confidentiality, legitimacy |
| 161–180 Changing environments | climatology, weather, troposphere, biosphere, hydrosphere, lithosphere, cryosphere, albedo, forcing, sequestration, acclimatisation, decarbonisation, vulnerability, richness, fragmentation, connectivity, tipping, threshold, cascade, perturbation |
| 181–200 Preparing for adult life | tenancy, lease, landlord, tenant, guarantor, warranty, guarantee, subscription, cancellation, renewal, dispute, mediation, arbitration, grievance, affordability, eligibility, declaration, notarisation, indemnity, redress |
List audit: 200 entries in 10 groups of 20. Every target word is unique within this list and assigned only once in the complete Age 1–16 collection of 3,200 words. Earlier words should still be reused in conversation. This audit concerns word selection, not a child’s development.
Ages 1–16: vocabulary series index · All vocabulary guides
Choose your next step
Institutions, ethical choices and disciplined analysis. Use the list as a reference, then choose the part of the guide that helps today.
Guide contents
1–5: Meanings and everyday use
6–10: More examples, questions and sources
“The results prove it works” sounds decisive. “The results show an association, but the groups differed before the comparison” tells you more. The second sentence identifies what was found and what still needs investigation.
This vocabulary bank offers language for reasoning, research, ethical choices and documents that affect everyday decisions. You might need counterexample in a discussion, confidentiality when contributing a personal story, or renewal when reading subscription terms. The useful word is the one that makes your meaning clearer.
Age fifteen is an editorial organising label. This is not a validated ranking, a developmental assessment or a requirement to master 200 words before your next birthday. Specialist entries such as jurisprudence, disequilibrium and operationalisation can remain reference words until you have a reason to explore them.
Start with a question you actually have. Find a relevant word, check its meaning in that context and try a sentence that somebody else can understand. Familiar words from earlier age lists remain welcome: the nonrepeat rule concerns the selected target entries, not conversation or practice. All scenes and sample wording below are invented illustrations.
Necessity concerns a condition that must be present for the stated result. Sufficiency concerns a condition that is enough to guarantee that result under the stated rule. The Stanford Encyclopedia of Philosophy discussion explores these distinctions and the complications of ordinary conditional language. A deliberately simple rule makes a useful starting point.
Imagine a puzzle with this complete rule: its gate is open exactly when switches A and B are both on. There are no other controls.
Four possible states in the invented puzzle
| Switch A | Switch B | Gate |
|---|---|---|
| Off | Off | Closed |
| Off | On | Closed |
| On | Off | Closed |
| On | On | Open |
A being on is necessary, but it is not sufficient by itself. B must also be on. Having both switches on is sufficient under this rule.
The third row is a counterexample to “Whenever A is on, the gate opens.” It supplies a case where the proposed condition holds but the promised result does not. One such case defeats that universal claim.
When reading an actual eligibility statement, ask: “Does meeting this condition guarantee acceptance, or does it only allow an application?” Check the complete conditions before answering. A short headline may omit a selection step. Write down the exact claim you are checking; changing “all” to “some” changes what would count against it.
Different arguments make different promises. In deductive reasoning, a valid argument cannot have all true premises and a false conclusion. Soundness adds that the premises really are true. Stanford’s teaching note on validity and soundness explains this distinction.
Consider: “Every file in this archive is read-only. This file is in the archive. Therefore, this file is read-only.” The conclusion follows from those premises. To establish that the argument is sound in a real situation, you would also need to check the premises. A neat structure cannot repair an inaccurate starting claim.
Induction supports a conclusion beyond the cases already observed. If the last several deliveries arrived before noon, you might expect the next one to do so. That expectation could still be wrong.
Abduction, in the sense discussed by the Stanford Encyclopedia of Philosophy, involves reasoning towards an explanation that best accounts for the evidence. Its conclusion can be revised. Philosophers disagree about exactly how “best” should be understood.
Imagine a projector showing a blank screen just after somebody changes its input setting. The wrong input is a plausible explanation. A power problem or another fault might also fit some of the evidence. “This explains the timing well” is more careful than “This must be the cause.”
A parsimonious explanation avoids unnecessary complications. Simplicity can be attractive, but it does not establish truth. Ask what each explanation predicts and what observation could distinguish the alternatives. You can then change your view for a stated reason, rather than defend your first explanation simply because it was yours.
Imagine a club notices that members who chose a reminder tool missed fewer deadlines. That observation does not, by itself, establish that the tool caused the difference. People who were already more organised might have been more likely to choose the tool and more likely to meet deadlines anyway.
Pre-existing organisation is a potential confounder in this invented example. It is a proposed explanation to investigate, not something the comparison has proved. The CDC’s epidemiology manual describes confounding as distortion of an association by another factor related to both the exposure and the outcome, rather than a consequence of the exposure.
In an observational comparison, investigators do not assign the intervention being studied. Participants may still receive or choose an intervention. That distinction appears in ClinicalTrials.gov’s study terminology. The club’s comparison observes choices people have already made.
Randomisation uses chance to assign participants to comparison groups. The National Cancer Institute explains its role in making intervention comparisons fairer. It does not guarantee that every characteristic will be perfectly balanced in a particular study.
Overclaim: “The reminder tool makes everyone reliable.”
More accurate: “In this comparison, users missed fewer deadlines. We have not established how much the tool contributed.”
Useful next question: “Were users and non-users different before they chose whether to use it?”
Observational evidence can be valuable. The point is to match the strength of the conclusion to the design and the available evidence. Naming a possible confounder opens a question; it does not automatically settle the question in the opposite direction.
A study can sound impressive while leaving its method unclear. Replace a broad label with a description of what was collected, how it was examined and what conclusion that procedure can support.
Quantitative information might include counts of missed deadlines. Qualitative information might include participants’ accounts of why a reminder was useful or irritating. NIH’s mixed methods resources describe combining and integrating these approaches. Numerical records and detailed accounts can answer different parts of a question; collecting both does not automatically make a study well designed.
Operationalisation turns a broad concept into a specified way of studying it. The NIH research glossary describes an operational definition in terms of the procedure used to measure a construct. For the invented club comparison, “reliability” is too broad. “Whether an agreed task was submitted by its recorded deadline” identifies something observable, although it captures only one part of reliability.
Write the missing decisions beside that definition. Who agreed the deadline? How are authorised extensions treated? What happens when the submission record is missing? These questions make the method inspectable. They also reveal why an apparent difference may depend on how a measurement was defined.
Preregistration records a research plan in a registry before the relevant research or analysis. The Center for Open Science explains how this distinguishes planned work from work developed after seeing results. It can also precede analysis of an existing dataset. New analyses remain possible; readers should be told which decisions changed.
For an ordinary project, drafting a question and a method before looking at results is useful practice. A dated notebook entry alone is not a formal preregistration. You can still preserve the original plan and explain revisions honestly: “We originally asked about deadlines; the comments raised a separate question about notification overload.”
Ethics vocabulary helps identify what matters when benefits, burdens and choices pull in different directions. It should make a decision easier to examine, rather than make its speaker sound morally superior.
Within research involving people, the US Belmont Report discusses respect for persons, beneficence and justice. Its treatment includes respecting autonomous decisions, considering benefits and harms, and examining how research burdens and benefits are distributed. This is a research ethics source, not a universal description of every country’s law.
Consider an invented decision about a community event. Organisers want feedback so that the next event is easier to attend. Their draft form requests names, home addresses and detailed reasons for leaving early, although they have not explained why those details are needed.
- Autonomy: Can contributors understand the request and make a meaningful choice about what to share?
- Beneficence: What useful change could the feedback support, and what burdens or discomfort might the request create?
- Confidentiality: Who would be able to see an identifiable response, and what promises could the organisers actually keep?
- Proportionality and minimisation: Is the amount and sensitivity of information requested appropriate to the purpose? Could a narrower question do the job?
A reasoned response might be: “We want to understand difficulties with the timetable. Let us ask about the timetable first and explain how responses will be used. We have not shown why home addresses are needed.”
That proposal names a purpose, identifies an avoidable burden and offers an alternative. Another person might raise an accessibility need the proposal misses. Listen for that possibility. Ethical discussion can improve a decision without producing a perfect answer or a single word that ends the conversation.
Rhetoric concerns how language works to communicate and persuade. A memorable phrase can help readers follow an argument. It can also conceal an uncertainty or leave an important word unexplained.
Try revising these invented statements. The aim is to give readers information they can use.
Three revisions that make a claim easier to examine
| Original wording | Problem to check | More precise wording |
|---|---|---|
| “The new system is better.” | Ambiguity: better in which respect? | “The new system takes fewer steps to submit a request. We have not compared its error rate.” |
| “There will be a service adjustment.” | A possible euphemism: a softer phrase hides the practical change. | “The counter will close an hour earlier on Fridays.” |
| “This proposal benefits everyone.” | A universal claim overlooks possible differences. | “This proposal reduces the entry fee. We still need to consider people who cannot use the booking method.” |
Equivocation occurs when an argument shifts between meanings of an expression in a way that misleads, as the Stanford Encyclopedia’s discussion of fallacies explains. Imagine an advertisement calling a service “free” to mean no subscription charge, then arguing that “free” means users give up nothing. The second meaning does not follow from the first; time and other burdens still need consideration.
When disagreeing, quote the claim accurately and explain the missing step. “Does ‘free’ here mean no payment, or no burden at all?” is a useful question. Calling someone’s whole position a fallacy without identifying the reasoning problem gives them little to answer.
An unfamiliar word in an agreement is a reason to slow down and ask a precise question. Its effect depends on the document and the applicable law. A vocabulary list cannot establish someone’s rights or obligations in a particular jurisdiction.
Imagine comparing two equipment-hire forms for a fictional event. You are practising document reading, not agreeing to either form.
- Renewal: Does the arrangement continue automatically, and on what terms?
- Cancellation: What action, deadline and possible charge does the document specify?
- Warranty or guarantee: What is promised, by whom, for how long and with what stated limits?
- Guarantor: What responsibility would this person take on, and in what circumstances?
- Indemnity: Which losses or claims does the clause address, and who would be responsible?
- Redress: What process is available if something goes wrong?
Mediation and arbitration also need context. For a specifically identified example, the US District Court for the Eastern District of Tennessee describes mediation as facilitated negotiation towards a solution the parties develop. Its description of arbitration involves an arbitrator’s binding decision. Its local rules govern how cases are referred. Those details must not be assumed to apply to another court, country or agreement.
Try asking, “Who decides the outcome here, and where does this document explain the process?” Keep the actual wording beside your paraphrase. If your explanation adds a promise the document does not make, revise it. For a real consequential agreement, resolve unclear terms with an appropriate local adviser before relying on your interpretation.
Do I need to use every word in conversation?
No. Some words may be useful mainly when reading a particular subject. Recognising albedo in a climate explanation has a different purpose from using cancellation in an everyday question. Choose vocabulary that serves your interests and immediate needs.
How can I tell whether I understand a word?
Try explaining it plainly, giving a fitting example and identifying a nearby meaning it should not be confused with. “Necessary” and “sufficient” provide a useful pair. If your example stops working when the conditions change, explain which conditions matter.
Does preregistration prove that a study is correct?
No. Recording a plan does not establish that its measurements, analysis or conclusions are right. Treat it as information about what was planned, alongside the other details needed to examine the work.
What if we disagree about the ethical answer?
Identify the point of disagreement. Are you predicting different consequences, prioritising different values or missing a practical alternative? You can explain those differences without assigning bad motives to the other person.
Should an adult replace every simple word with a specialist one?
No. Ask what the young person means, then offer a word when it adds precision. “Which part seems unfair?” is often a better opening than demanding an abstract label. A clear ordinary sentence can communicate more effectively than an overloaded technical one.
The linked references support particular distinctions, not an age-based vocabulary ranking. Examples, questions and practice suggestions are original editorial illustrations.
- Stanford Encyclopedia: necessary and sufficient conditions; abduction; equivocation; Stanford teaching note: validity and soundness.
- CDC: confounding; ClinicalTrials.gov: study terminology; NCI: randomisation.
- NIH OBSSR: mixed methods resources; NIH: operational definitions; Center for Open Science: preregistration.
- HHS: Belmont Report, for research ethics; Eastern District of Tennessee: mediation and arbitration, for that court’s description.
Continue with useful words, at your own pace
This compact collection assigns new target words to each age band. It complements the larger reference banks below. Familiar words remain part of every later conversation.
Choose another age
Age 1 · Age 2 · Age 3 · Age 4 · Age 5 · Age 6 · Age 7 · Age 8 · Age 9 · Age 10 · Age 11 · Age 12 · Age 13 · Age 14 · Age 16
Broader vocabulary resources
- The Age 15 reference bank of 2,000 words — a wider reference when you want more word choices.
All 16 guides in this collection are now published, with 3,200 distinct target entries across Ages 1–16. The nonrepeat rule applies within this Essential 200 collection; other eduKate vocabulary collections may include the same useful words.