Lexical
density
Linguistic
complexity
Readability
Lexical density is “the kind of complexity
that is typical of written language”
(Halliday, 1985, p.62)
Lexical
density
Linguistic
complexity
Readability
Readability "depends on several factors including
the average length of sentences, the number of
new words contained, and the grammatical
complexity of the language used in a passage.”
(Richards, et al.,1992, p.306)

Identify the changes of lexical density and readability;

Find out the relationship between lexical density,
readability and text levels;

Discover the consistency between the measurements
of lexical density and readability.
1.
How do lexical density and readability change across
levels in the selected texts in English textbooks?
2.
What is the relationship between lexical density,
readability and text levels?
3.
What is the correlation between the methods adopted to
access lexical density and readability?
How to measure LEXICAL DENSITY?
1. Ure’s method:
Lexical density =
the number of lexical items x 100
the total words
(Ure, 1971; Halliday, 1985)
When you heat a liquid, it can change into gas.
How to measure LEXICAL DENSITY?
1. Ure’s method:
Lexical density =
the number of lexical items x 100
the total words
(Ure, 1971; Halliday, 1985)
When you heat a liquid, it can change into gas.

Lexical density: 40%
How to measure LEXICAL DENSITY?
2. Halliday’s method:
Lexical density =
the number of lexical items
the number of clauses
(Halliday, 1985)
When you heat a liquid, it can change into gas.

Lexical density: 2

Grammatical items:
Determiners, pronouns, most prepositions, conjunctions,
some classes of adverb and finite verbs. (Halliday, 1985)

Lexical items:
Nouns, verbs, adjectives and adverbs are the four word classes
belonging to lexical items (T.Le, Yue, & Le, 2011).
Some kinds of lexical items and grammatical
items were determined differently by linguists
and researchers in literature
(To, V. et al., 2013)

Halliday (1985) /Ure (1971): Phrasal verbs: give up, eat out

O’Loughlin (1995): All prepositions, conjunctions, quantifiers

Castello (2002, cited in Castello, 2008, p.56-57) :
3-word sequence prepositions: in view of, in terms of
open-class quantifiers: heaps of, a great deal of
complex conjunctions and subordinators: provided that,
regardless of
“it does not matter exactly where we draw
the line provided we do it consistently”.
(Halliday, 1985, p.63)
 Halliday
(1985)
 O’Loughlin
(1995)
 Ure (1971)
 Castello (2002)
(To, V. et al., 2013b)
Word Class
All NOUNS
• university, David, Apple
Notes
A compound noun /
phrasal verb /compound
All LEXICAL
VERBS
All
ADJECTIVES
• Eat, read, think
adjective - a lexical item
E.g. long-term, eat out,
old, beautiful, useful
good-looking
Two kinds • Manner adverbs: quickly, beautifully
of ADVERBS
• Sentence adverbs: honestly, fortunately
Word class
All
PRONOUNS
• Personal pronouns
Examples
I, you, she, them, one
• Demonstrative pronouns this, that, these, those
• Possessive pronouns
mine, yours, his, hers, its,
• Reflexive pronouns
myself, yourself, himself
• Indefinite pronouns
nothing, anyone, another
Word class
All
DETERMINERS
Examples
• Articles
a, an, the
• Possessive
my, your, his, her
adjectives
• Quantifiers
some, any, many, few,
• Numerals
one, sixteen, second, third
Word class
All FINITE VERBS • Be
Examples
am, is, are, was, were, been
• Do
do, does, did
• Have
have, has, had
• Modals
can, may, probably, certainly
Be, Do, Have as main verbs
Lexical items
• I am a student.
Be, Do, Have as auxiliaries
Grammatical items
• I am talking.
He was beaten.
• I have cereal for breakfast.
• You have done a good job.
• The student did his homework. • Did the student do his
homework?
Word class
Some
• Temporal adverbs
classes of
ADVERBS
• Locative adverbs
Examples
now, then, today, always, later,
beforehand, afterwards
here, there, below, above,
outside, upstairs, indoors
• Degree adverbs
very, too, so, rather, quite
• Negative and
Interrogative ADV
Not, never, when, where, how
Word class
Examples
All CONJUNCTIONS
and, but, however, therefore
All PREPOSITIONS
in, at, of, with, between
All DISCOURSE MARKERS
Oh, well, you know, I mean
All INTERJECTIONS
Oh, my god, my godness, gosh
All REACTIVE TOKENS
yes, no, O.K, right, mm
“It is not always easy, however, to recognise what a
clause is. Again, for comparative purposes, the main
requirement is consistency”
(Halliday, 1985, p.67)
(Halliday & Mathiessen, 2004; Lukin, 2013)

Hypotactic clauses:
|||Now, I often eat this soup ||when I am tired or worried.|||

Paratactic clauses:
|||Now, I often eat this soup || and it helps me feel better.|||
|||These students often feel overwhelmed ||and will put off doing
many things they need to.|||

Non-defining relative clauses:
|||The only Asian country to adopt it at that time was the Philippines,
||which the Spanish invaded in the sixteenth century.|||
(Humphrey et al., 2012; Lukin, 2013)

Defining relative clauses:
|| People everywhere appreciate individuals [[who are
interested in getting to know them and learn about their ways of
doing things]]||

Interrupting clauses
||They had to be transported, [[in order to reach safety]],
through floodwaters.||

Non-finite clauses
|| [[ To be successful, and to enjoy your experience abroad,]]
you must be flexible, open-minded, and both eager and willing
to learn new ways of doing things. ||
How to measure READABILITY?
3. Flesh’s method:
Reading Ease = 206.835 – 0.846 wl – 1.015 sl
(Flesch, 1948)
Flesch Reading Ease
0-30
30-50
50-60
60-70
70-80
80-90
90-100
Description of style
Very difficult
Difficult
Fairly difficult
Standard
Fairly easy
Easy
Very easy
How to measure READABILITY?
3. Flesh’s method:
Reading Ease = 206.835 – 0.846 wl – 1.015 sl
(Flesch, 1948)
Flesch Reading Ease
0-10
10-20
20-30
30-40
40-50
50-70
70-100
Description of style
Very easy
Easy
Fairly easy
Standard
Fairly difficult
Difficult
Very difficult
Elementary
Text 1
Preintermediate
Text 2
Intermediate
Text 3
Upperintermediate
Text 4
 Lexical items
 Total words
 Ranking
clauses
 Halliday
and Ure’s formulas
 Flesch Reading
Ease Scale
 Correlation
(To, V. et al., 2013a)

LEXICAL DENSITY and READABILITY among chosen reading
texts in English textbooks
Texts
Total words
Lexical words
Ranking clauses
Ure’s
method
Lexical Halliday’s
density method
Flesch’s
method
1
2
3
4
(Elementary)
(Preintermediate)
(Intermediate)
(Upperintermediate)
173
84
24
160
73
14
162
61
15
165
75
11
49%
46%
38%
46%
3.5
5.2
4.1
6.8
25
53
48
44

The changes of LEXICAL DENSITY across levels
Figure 1: Ure's method
60%
50%
49%
46%
46%
38%
40%
30%
20%
10%
0%
Text 1
Text 2
Text 3
Text 4

The changes of LEXICAL DENSITY across levels
Figure 2: Halliday's method
8
6.8
7
6
5.2
5
4
4.1
3.5
3
2
1
0
Text 1
Text 2
Text 3
Text 4

The changes of READABILITY across levels
Figure 3: Flesh's method
60
53
48
50
44
40
30
25
20
10
0
Text 1
Text 2
Text 3
Text 4

The relationship between LEXICAL DENSITY, READABILITY
and TEXT LEVELS
Levels
Lexical density
Readability
Ure’s method
Halliday’s
method
Flesh’s method
Elementary
the highest
the lowest
the easiest
Pre-intermediate
high
high
the most
difficult
Intermediate
the lowest
high
fairly difficult
UpperIntermediate
high
the highest
fairly difficult

The correlation between the methods employed
Texts
Lexical density
Ure’s
method
Halliday’s
method
Flesch’s
method
1
49
3.5
25
2
46
5.2
53
3
38
4.1
48
4
46
6.8
44
Correlation coefficient
Halliday &
Ure’s method
Halliday &
Flesch’s
method
Flesh & Ure’s
method
0.1
0.5
-0.6

Ure’s method revealed that lexical density did not
match the text levels and text difficulty.

In contrast, Halliday’s method of lexical density
corresponded to the text levels and readability.

As for Flesh Reading Ease, readability increased from
low to high. However, the highest level did not entail
the highest readability.
1. Ure’s method:

Lexical density did not match the text levels and text difficulty
(Text 1 was the most dense; Text 3 was the least dense).
the ILLOGICAL result

The texts chosen for the lexical density analysis in the four
books may not necessarily represent the complexity for each of
the books.

In this study, the density is only a factor for judging
complexity.
2. Halliday’s method:

Lexical density corresponded to the text levels and readability.
(Text 1 was the least dense; Text 4 was the most dense)
Halliday-based findings are LOGICAL

It may convince us that Halliday's approach in measuring lexical
density is MORE CONSISTENT, thus more powerful.
3. Flesh’s Reading Ease Scale:

Readability increased from low to high. However the highest level
did not entail the highest readability.
(Text 2 was the most difficult)

Lexical density alone cannot fully explain about readability.

HALLIDAY 'S METHOD is CONSISTENT and applies well
in measuring lexical density in relation to other
grammatical features such as nominalisation,
grammatical metaphor, etc.

CONSISTENCY is important in analysing lexical density .

LEXICAL DENSITY is only ONE ASPECT of text
complexity. Thus it alone cannot completely explain
about readability.

This is only 'EXPLORATORY‘ study.
• The findings support HALLIDAY’S THEORY.
• Regarding URE’S METHOD and FLESH READING EASE
It raises more questions than answering .

Sentence structure

Nominalisation

Grammatical metaphor

Thematic structure













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(Eds), Innovative trends in Language and literacy education in a global discourse. Malaysia: Pearson
Longman. (in press)
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Vinh To - University of Tasmania
[email protected]
Vinh Tô
@VinhTTo