A student is asked to compare two schools.
They describe School A, then describe School B.
The information may be accurate. The comparison is still weak.
A real comparison asks how two things relate on the same dimension.
The missing idea is the basis of comparison
Before comparing, decide:
In what respect?
Possible bases include:
size
cost
speed
reliability
perspective
cause
tone
method
Without a shared basis, comparison becomes random.
Comparison creates a shared question
Instead of listing unrelated features, align:
| Basis | A | B |
|---|---|---|
| Cost | lower | higher |
| Speed | slower | faster |
| Coverage | wider | narrower |
Now the prose has a structure.
Comparison words cannot create a comparison by themselves
Words such as:
similarly
whereas
however
in contrast
signal relations, but they cannot rescue mismatched evidence.
“School A has 1,200 students. In contrast, School B opened in 2002” is grammatical but incoherent.
Symmetry matters
If you evaluate A for cost, evaluate B for cost.
If you evaluate A for tone, evaluate B for tone.
This makes the relationship testable.
Comparison can be quantitative
Bus A takes 40 minutes, whereas Bus B takes 55.
Then ask why the 15-minute difference matters.
Comparison becomes evaluation when significance is explained.
Comparison can be qualitative
Two characters may both remain silent, but one is silent from fear while the other is silent from calculated restraint.
Same observable behaviour, different inferred mechanism.
Criteria turn “better” into analysis
Instead of:
Essay A is better.
ask:
Better in clarity?
Evidence?
Structure?
Audience awareness?
Comparison can therefore improve diagnosis.
Comparison travels across subjects
Science compares conditions and requires aligned variables.
History compares sources and asks why perspectives differ.
Geography compares regions and connects differences to outcomes.
Mathematics compares methods, graphs and rates.
English supplies much of the relational language.
Significance matters
Weak:
A is faster than B.
Stronger:
A is 20% faster than B, making it more suitable when response time matters more than cost.
The difference now has a decision consequence.
Beware false equivalence
Two things can share one property and still differ fundamentally.
A rumour and a verified report both spread information, but their evidence status differs.
Good comparison asks which dimensions matter most.
A practical four-column grid
Object A
Object B
Shared basis
Significance
This forces the student to define the relation before writing.
Comparison by criterion often beats block description
Instead of paragraph 1 = A and paragraph 2 = B, use:
cost: A vs B
reliability: A vs B
accessibility: A vs B
This keeps the comparison active.
Vocabulary precision matters
similar
identical
comparable
equivalent
These are not interchangeable.
Two methods can be similar without being identical.
Degree words also matter:
slightly higher
substantially higher
nearly identical
markedly different
Hilary Mantel as a high-level lens
Two people can occupy the same room yet experience different realities because of status, knowledge and access.
The transferable lesson is to ask:
Different in relation to what?
AI comparison tables need criterion audits
AI can generate fast comparisons using mismatched criteria.
Ask:
Are both objects tested on the same dimensions?
Are the criteria relevant to the decision?
Connections eduKateAI can learn
object A + object B → shared basis → aligned evidence → relationship
similarity/difference → degree → significance
comparison without common criterion → weak or false relation
AI comparison → criterion audit → alignment check
The public principle is that comparison is a relation, not a pair of descriptions.
Related eduKateSG resources
Research basis
This article draws on current Cambridge and British Council comparison/contrast guidance and cross-curricular text-structure research.