How Do You Synthesize Studies That Use Different Definitions of the Same Concept?

What If the Studies Use the Same Term but Mean Different Things?

You are reviewing the literature on a concept such as student engagement, resilience, digital literacy, well-being, trust, or academic success. The papers appear to address the same topic, so grouping their findings seems reasonable. Then you read the definitions carefully.

One study defines engagement as observable participation. Another includes emotional involvement and cognitive investment. A third treats engagement largely as time spent using a learning platform. The terminology is shared, but the concepts are not necessarily identical.

This creates a synthesis problem. If you combine the studies as though they investigated precisely the same construct, you may manufacture agreement or disagreement that disappears once the definitions are examined. Yet separating every definition into its own literature can obscure genuine conceptual overlap.

The task is therefore not to decide which definition is universally correct. It is to determine how much conceptual territory the definitions actually share and make that structure visible in your synthesis.

Synthesize the Shared Concept, but Preserve the Differences

Conceptual Equivalence Comes Before Evidential Comparison

A shared label is not evidence of a shared definition

Research constructs are conceptual entities. Many cannot be observed directly, so researchers define what they mean by the construct and then connect that definition to observations, indicators, instruments, or other forms of evidence. Construct validity consequently depends partly on whether interpretations of measurements are defensible in relation to the intended construct. Contemporary measurement literature emphasizes that clear conceptualization is fundamental to this process.

This matters for literature synthesis because terminology can create an illusion of comparability. Two articles may both investigate “engagement,” while one conceptualizes it primarily as behavior and another treats it as a multidimensional construct involving behavioral, emotional, and cognitive components.

The reverse can happen too. Researchers may use different labels for concepts that substantially overlap. A synthesis based only on keywords or variable names can therefore split related evidence while combining evidence that is conceptually distinct.

Compare the content of the definitions

Instead of asking whether two definitions are worded identically, ask what each definition includes and excludes. Definitions often differ along dimensions that materially affect the interpretation of findings.

For each study, identify the conceptual components included in the definition. A definition of student engagement, for example, might include attendance, participation, persistence, emotional involvement, cognitive effort, interaction, or some combination of these. Another definition might deliberately exclude several of those components.

You can then ask whether the definitions have:

• substantial overlap: the same central concept is present despite differences in wording or emphasis;
• partial overlap: the definitions share a core but include different additional dimensions;
• nested relationships: one definition is substantially broader than another;
• boundary differences: the definitions disagree about what belongs inside the construct;
• fundamental differences: the shared label conceals constructs that are difficult to treat as equivalent.

This conceptual mapping is related to, but different from, identifying broader themes in the literature. Here, you are examining the boundaries of a particular concept before deciding which findings can reasonably speak to one another.

Look for the shared conceptual core

When definitions overlap, the most defensible synthesis often begins with their common denominator.

Suppose three studies define academic resilience differently:

• Study A emphasizes persistence after academic setbacks.
• Study B includes persistence, adaptation, and recovery.
• Study C defines resilience more broadly as successful functioning despite academic adversity.

These definitions are not interchangeable, but they may share a core idea involving adaptive responses to academic difficulty. You can synthesize evidence concerning that shared core while preserving differences concerning persistence, recovery, adaptation, and successful functioning.

This is more defensible than silently selecting one definition and treating every study as though it used that definition.

Do not collapse broader and narrower definitions automatically

One common relationship between definitions is nesting. A narrow definition may represent one component of a broader construct.

Imagine that one study defines digital literacy as the ability to locate and evaluate digital information, while another includes information evaluation, content creation, communication, safety, and problem solving. Evidence from the first study may inform one part of the broader conception, but it cannot automatically support claims about all of its dimensions.

Definition differences can explain apparently conflicting findings

Conceptual variation is not merely a nuisance to mention in a limitations paragraph. Sometimes it helps explain why studies reach different conclusions.

Suppose studies using a behavioral definition of engagement consistently report a relationship with an educational intervention, while studies using emotional definitions report weak or inconsistent relationships. Writing that “the evidence on engagement is mixed” loses useful information.

A stronger synthesis might conclude that the apparent inconsistency is patterned by how engagement is conceptualized: evidence is more consistent for behavioral engagement than for emotional engagement.

That does not prove that the definition caused the difference. Other features of the studies may also differ. But the definitional distinction becomes a plausible organizing explanation that should be examined alongside design, measurement, population, and context.

Definition and measurement are related, but they are not the same problem

A study's conceptual definition concerns what the construct means. Operationalization concerns how researchers represent or observe it. Those questions should not be collapsed.

A construct can be defined similarly across studies but measured in different ways. Conversely, apparently similar measures can be interpreted through different conceptual frameworks. Measurement scholarship treats validity as concerning the interpretations supported by evidence and theory, rather than as a permanent property attached to an instrument itself.

Build your synthesis at the level the evidence can support

Once you understand the definitions, decide what level of synthesis is defensible.

This approach also helps you judge what the literature actually establishes. A conclusion may be robust across several definitions, limited to one conceptualization, or impossible to state confidently because the literature has never converged on what the focal concept means.

Conceptual heterogeneity can itself be a finding

Researchers sometimes treat inconsistent definitions as an inconvenience to be cleaned up before the “real” synthesis begins. In some literatures, however, the inconsistency is substantive information.

If authors repeatedly invoke the same construct while assigning substantially different meanings to it, the field may lack conceptual consolidation. A recent systematic review of intellectual humility, for example, discusses substantial definitional heterogeneity and describes previous work that organized multiple definitions into conceptual dimensions rather than treating them as interchangeable.

Your review can therefore report not only what studies found, but also how the field has constructed the phenomenon it claims to study. This may reveal why apparently accumulated evidence remains difficult to interpret.

From Four Definitions to One Defensible Synthesis

Common Ways Definition Differences Distort a Literature Review

Make the Definitions Part of the Synthesis, Not a Footnote to It

When you encounter several definitions of the same concept, resist two extremes. Do not flatten them into a single construct merely because the terminology matches, but do not fragment the literature into isolated categories at the first sign of variation either.

Start by extracting each study's definition and identifying its conceptual components. Then compare the boundaries: what is common, what is unique, what is broader or narrower, and what may actually represent a different construct.

Next, inspect whether the empirical findings change with those conceptual differences. This is particularly important when you are trying to make sense of conflicting evidence. What looks like disagreement among studies may partly reflect disagreement about what phenomenon is being studied.

Your language should also reflect the resulting level of certainty. If conceptual inconsistency prevents a clean conclusion, avoid making the literature sound more settled than it is. Sometimes the defensible conclusion is that evidence exists across several related conceptualizations, but a claim about the overarching construct remains uncertain.

Before Combining Studies Under One Concept, Check:

Questions About Synthesizing Different Definitions

Do Not Let a Shared Label Manufacture a Shared Construct

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