Calculating the Difficulty of Articulation in English Words

Words are not all equally easy to pronounce. Some words, such as me, go, or sun, are physically simple because they require only a few speech movements. Other words, such as strengths, sixths, or crisps, are harder because they require many rapid movements of the tongue, lips, jaw, and vocal cords.

The difficulty of pronouncing a word can be studied through articulation, which is the physical process of producing speech sounds. Articulation involves the movement and coordination of several parts of the vocal tract, including:

1. the lips
2. the tongue
3. the teeth
4. the alveolar ridge
5. the hard palate
6. the soft palate
7. the jaw
8. the vocal cords

This article presents a method for calculating the articulatory difficulty of English words based on the physical movement needed to produce them. The formula is not a universal linguistic standard, but it is a practical scoring system that can be used to compare words.

Basic Idea

The difficulty of a word depends on several physical factors.

A word is usually harder to pronounce when it has:

• many sounds
• difficult consonant clusters
• rapid changes in tongue or lip position
• changes between voiced and voiceless sounds
• rare or complex sounds
• awkward transitions between sounds

For example, the word cat is relatively easy. It has three sounds:

/k/ /æ/ /t/

The mouth moves from the back of the tongue for /k/, to an open vowel /æ/, then to the alveolar ridge for /t/. This requires some movement, but the word is short and common.

The word strengths is harder. It may be pronounced approximately as:

/strɛŋkθs/

This word contains several consonants close together, including /s/, /t/, /r/, /ŋ/, /k/, /θ/, and /s/. It requires fast tongue movement, a back-of-mouth nasal sound, and a dental fricative. This makes it physically more difficult.

A Proposed Articulation Difficulty Score

We can create a score called the Articulation Difficulty Score, or ADS.

The score is based on five main factors:

1. Number of phonemes
2. Individual sound difficulty
3. Movement between sounds
4. Consonant cluster difficulty
5. Voicing and airflow changes

The general formula is:

ADS = P + S + M + C + V

Where:

• P = phoneme count score
• S = sound difficulty score
• M = movement transition score
• C = consonant cluster score
• V = voicing and airflow change score

A higher score means the word is harder to articulate.

Step 1: Phoneme Count Score

The first part of the score is based on the number of phonemes in the word.

A phoneme is a meaningful speech sound. For example, the word ship has three phonemes:

/ʃ/ /ɪ/ /p/

The word has four letters, but only three sounds.

The formula for phoneme count is:

P = number of phonemes

Examples:

me = /m i/ = 2 phonemes, so P = 2

cat = /k æ t/ = 3 phonemes, so P = 3

strengths = /s t r ɛ ŋ k θ s/ = 8 phonemes, so P = 8

Longer words usually require more physical effort, so they receive a higher score.

Step 2: Individual Sound Difficulty Score

Some sounds are physically harder to produce than others.

For example, /m/ is easy because the lips simply close and the vocal cords vibrate. However, /θ/, as in think, is harder because the tongue must be placed between or near the teeth while air flows through a narrow space.

We can assign each sound a difficulty value.

Easy sounds: 1 point

These sounds require simple or common movements:

/p, b, m, t, d, n, k, g, f, v, s, z, h, w, j/

Most basic vowels also receive 1 point:

/i, ɪ, e, ɛ, æ, ɑ, ɔ, o, ʊ, u, ə/

Medium sounds: 2 points

These sounds require more precise tongue shaping or airflow control:

/ʃ, ʒ, tʃ, dʒ, l, r, ŋ/

Diphthongs also receive 2 points because the mouth moves during the vowel:

/aɪ, aʊ, ɔɪ, eɪ, oʊ/

Difficult sounds: 3 points

These sounds are especially difficult for many speakers because they require precise tongue placement or controlled friction:

/θ, ð/

So the sound difficulty score is:

S = sum of the difficulty values of all phonemes

Example: think = /θ ɪ ŋ k/

/θ/ = 3

/ɪ/ = 1

/ŋ/ = 2

/k/ = 1

So:

S = 3 + 1 + 2 + 1 = 7

Step 3: Movement Transition Score

A word becomes harder when the mouth has to move quickly between very different positions.

For example, moving from /m/ to /b/ is easy because both sounds use the lips. But moving from /p/ to /k/ is harder because the mouth moves from the lips to the back of the tongue.

To calculate this, we can group consonants by place of articulation.

Main places of articulation

Bilabial: both lips

Examples: /p, b, m/

Labiodental: lip and teeth

Examples: /f, v/

Dental: tongue and teeth

Examples: /θ, ð/

Alveolar: tongue near ridge behind teeth

Examples: /t, d, n, s, z, l/

Postalveolar: tongue slightly farther back

Examples: /ʃ, ʒ, tʃ, dʒ, r/

Palatal: tongue near hard palate

Example: /j/

Velar: back of tongue

Examples: /k, g, ŋ/

Glottal: vocal cords

Example: /h/

Vowels can be grouped by height and backness, but for a simple system, vowels can be treated as a central open movement between consonants.

Transition scoring

For each pair of neighboring phonemes, assign a movement score:

• 0 points = same or very similar mouth position
• 1 point = small movement
• 2 points = medium movement
• 3 points = large movement

The formula is:

M = sum of transition scores between neighboring phonemes

Example: map = /m æ p/

/m/ to /æ/: medium movement = 2

/æ/ to /p/: medium movement = 2

So:

M = 4

Example: kick = /k ɪ k/

/k/ to /ɪ/: small or medium movement = 1

/ɪ/ to /k/: small or medium movement = 1

So:

M = 2

This suggests that map may involve more visible mouth movement, while kick stays closer to the back of the mouth.

Step 4: Consonant Cluster Score

A consonant cluster is a group of consonants with no vowel between them.

Examples:

stop begins with /st/

play begins with /pl/

street begins with /str/

texts ends with /ksts/

Consonant clusters increase difficulty because the speaker must move quickly between consonants without the easier opening movement of a vowel.

The formula for cluster difficulty is:

• C = 2 × number of extra consonants in each cluster

This means:

a 2-consonant cluster adds 2 points

a 3-consonant cluster adds 4 points

a 4-consonant cluster adds 6 points

Another way to write it:

C = 2 × (cluster length − 1)

for each consonant cluster.

Example: stop = /s t ɑ p/

The beginning cluster is /st/.

Cluster length = 2

• C = 2 × (2 − 1)
• C = 2

Example: street = /s t r i t/

The beginning cluster is /str/.

Cluster length = 3

• C = 2 × (3 − 1)
• C = 4

Example: strengths = /s t r ɛ ŋ k θ s/

It has:

beginning cluster /str/ = 4 points

ending cluster /ŋkθs/ = 6 points

So:

• C = 10

Step 5: Voicing and Airflow Change Score

Some words require quick changes between voiced and voiceless sounds.

A voiced sound uses vibration of the vocal cords. Examples include:

/b, d, g, v, z, m, n, l, r/

A voiceless sound does not use vocal cord vibration. Examples include:

/p, t, k, f, s, θ, ʃ, h/

Switching quickly between voiced and voiceless sounds adds difficulty.

The formula is:

V = number of voicing changes between neighboring consonants

Example: absent = /æ b s ə n t/

The consonant sequence includes:

• /b/ = voiced
• /s/ = voiceless
• /n/ = voiced
• /t/ = voiceless

There are several voicing changes, so the word gets a higher V score.

Airflow changes can also matter. Stops, fricatives, nasals, and liquids use different airflow patterns.

For a simple version, add:

+1 point each time the word switches between major manner types

Major manner types include:

stop: /p, b, t, d, k, g/

fricative: /f, v, θ, ð, s, z, ʃ, ʒ, h/

nasal: /m, n, ŋ/

liquid/glide: /l, r, w, j/

vowel

This gives a more complete version:

V = voicing changes + airflow/manner changes

Full Formula

The full formula is:

ADS = P + S + M + C + V

Where:

• P = number of phonemes
• S = sum of individual sound difficulty values
• M = sum of movement transition values
• C = consonant cluster penalty
• V = voicing and airflow change penalty

Scoring Guide

After calculating the total score, the word can be placed into a difficulty level.

ADS 1–10: Easy

These words are short and require simple movements.

Examples:

me

go

sun

cat

ADS 11–20: Moderate

These words have more sounds, some movement changes, or simple clusters.

Examples:

flower

walking

problem

teacher

ADS 21–35: Difficult

These words may contain several consonants, difficult sounds, or larger movement changes.

Examples:

street

plastic

question

growth

ADS 36 and above: Very difficult

These words often have complex clusters, difficult sounds, or many rapid transitions.

Examples:

strengths

sixths

texts

crisps

Example Calculation 1: “Cat”

The word cat is pronounced:

/k æ t/

Step 1: Phoneme count

There are 3 phonemes.

P = 3

Step 2: Sound difficulty

/k/ = 1

/æ/ = 1

/t/ = 1

S = 3

Step 3: Movement transitions

/k/ to /æ/ = 2

/æ/ to /t/ = 2

M = 4

Step 4: Consonant clusters

There are no consonant clusters.

C = 0

Step 5: Voicing and airflow changes

The word moves from stop to vowel to stop.

V = 2

Final score

• ADS = P + S + M + C + V
• ADS = 3 + 3 + 4 + 0 + 2
• ADS = 12

So, cat has an articulation difficulty score of 12, which is moderate but still simple.

This scoring method can be useful for:

1. comparing easy and difficult words
2. studying pronunciation problems
3. teaching English learners
4. speech therapy practice
5. analyzing tongue twisters
6. designing pronunciation exercises
7. measuring the physical complexity of English words

However, the score is only an estimate. Actual pronunciation difficulty can vary depending on the speaker’s first language, accent, age, speech habits, and physical ability. For example, /θ/ may be very difficult for speakers whose first language does not have that sound, but easier for native English speakers who use it every day.