What is the difference between a slip and a mistake?

A slip is an execution failure in which a correct plan is carried out incorrectly, such as performing the right action on the wrong object, whereas a mistake is a planning failure in which the chosen course of action is itself wrong.

Why standardize patient safety terminology at all?

Without agreed definitions, incident reports and studies cannot be compared or aggregated reliably, so standardized classifications such as the International Classification for Patient Safety were developed to make safety data interoperable.

Error Taxonomy and Definitions

Error taxonomy and definitions concern the shared vocabulary used to describe failures and harm in health care. Because terms such as error, mistake, slip, near miss, and adverse event have been used inconsistently across studies and reporting systems, the field has developed formal definitions and classifications so that incidents can be compared and counted reliably. A central distinction is between the type of error (how the failure happened) and its outcome (whether and how the patient was harmed).

Definition

Error taxonomy is the systematic classification of failures in health care by their nature, mechanism, and outcome, supported by agreed definitions that distinguish errors, near misses, and adverse events.

Scope

This topic covers the conceptual building blocks of patient safety terminology: the difference between errors and adverse events, categories of human error, the notion of near misses, and standardized frameworks such as the World Health Organization's International Classification for Patient Safety. It is a reference and educational treatment of how harm is named and categorized, not a reporting procedure or clinical guidance.

Core questions

How do errors, near misses, and adverse events differ, and why does the distinction matter for measurement?
What categories of human error (such as slips, lapses, and mistakes) are commonly used?
How does a standardized classification improve the comparability of safety data across settings?

Key concepts

Error of execution versus error of planning
Slips, lapses, and mistakes
Near miss (close call)
Adverse event and harm
Incident type versus contributing factors
Preventable versus non-preventable harm

Key theories

Generic Error-Modelling System (GEMS): Reason's cognitive taxonomy separates skill-based slips and lapses (execution failures) from rule-based and knowledge-based mistakes (planning failures), distinguishing errors that occur during correct intentions from those arising from flawed intentions; it grounds much of the vocabulary used to classify human error in health care.

Mechanisms

Taxonomies typically separate the cognitive origin of an error from its consequences. Errors of execution (slips and lapses) occur when a correct plan is carried out incorrectly, whereas errors of planning (mistakes) occur when the chosen plan is wrong even if executed as intended. Standardized frameworks such as the International Classification for Patient Safety then layer additional dimensions, including incident type, contributing factors, degree of harm, and mitigating actions, so that an event can be coded consistently rather than described in free text.

Clinical relevance

Precise definitions allow clinicians, researchers, and organizations to communicate about safety without ambiguity and to compare rates of harm across institutions. This topic explains terminology and classification; it does not prescribe how to manage individual incidents or patients.

Evidence & guidelines

The World Health Organization's International Classification for Patient Safety, summarized by Runciman and colleagues, provides an internationally agreed conceptual framework and set of preferred terms for patient safety incidents. The Institute of Medicine's To Err Is Human popularized the working definition of error as the failure of a planned action to be completed as intended or the use of a wrong plan, definitions that remain widely cited.

History

Early reporting systems used heterogeneous terms that made aggregation difficult. James Reason imported cognitive psychology's distinctions among slips, lapses, and mistakes into safety science, and the Institute of Medicine's 2000 report consolidated working definitions for a clinical audience. The World Health Organization's classification effort, reported in 2009, then sought an international standard vocabulary so that incident data could be pooled and compared.

Debates

Should classification focus on the error or on the harm?: Some frameworks organize data around the type of error and its causes, while others foreground the outcome and degree of harm; the choice shapes what gets counted and can produce divergent pictures of safety, so harmonizing the two remains a design tension in classification systems.

Key figures

James Reason
William Runciman
Lucian Leape

Seminal works

reason-2000
runciman-2009
kohn-corrigan-2000

Frequently asked questions

What is the difference between a slip and a mistake?: A slip is an execution failure in which a correct plan is carried out incorrectly, such as performing the right action on the wrong object, whereas a mistake is a planning failure in which the chosen course of action is itself wrong.
Why standardize patient safety terminology at all?: Without agreed definitions, incident reports and studies cannot be compared or aggregated reliably, so standardized classifications such as the International Classification for Patient Safety were developed to make safety data interoperable.