TH, unvoiced

The th of thin, bath and think — made with breath, no voice. Spelled identically to its voiced twin.

Digraphs

th DIGRAPH_TH_01

Useful pattern · Medium reliability · Very common · Beginner · Reading

/θ/ unvoiced th: thin, bath, think

Where Wiggler teaches it: Skill 3: Consonant Digraphs

Child explanation

Put your tongue between your teeth and blow. That is the th in thin and bath.

The rule

T and h together make one sound. The unvoiced version — no buzz in the throat — appears in most content words: thin, thick, think, three, bath, mouth, teeth.

What is really going on

English distinguishes /θ/ and /ð/ as separate phonemes but spells both th, so the spelling carries no information about which one a word takes. The distribution is largely lexical, with one useful generalisation: function words — the, this, that, these, those, them, then, there, they, though — are voiced, and most content words are unvoiced.

Position in the word

Beginning of a word — Unvoiced in content words. For example: thin, think, three, thumb.
End of a word — Almost always unvoiced. For example: bath, mouth, teeth, with, path.

Examples

Easy examples

thin, think, bath, teeth, three

More examples

thick, thumb, thing, thank, throw, mouth, path, north, math, cloth, birthday

Pseudo-words

Made-up words that follow the rule. A child who reads these has the pattern rather than the vocabulary.

thab, thesp, flanth

Contrast pairs

thin versus this — Unvoiced versus voiced — identical spelling, different sound.
tin versus thin — Single letter versus digraph.
three versus tree — The pair children find hardest to hear.

Decodable sentences

I think my teeth are thin.
Throw the thick cloth in the bath.
Thank you for the three things.

Common reading mistakes

thin: a child reads /tɪn/, where the word is /θɪn/. th produced as /t/.
three: a child reads /friː/, where the word is /θriː/. th produced as /f/, a very common developmental substitution.
that: a child reads /θæt/, where the word is /ðæt/. Unvoiced used where the word is voiced.

Do not teach it like this

Marking a child wrong for saying /f/ or /t̪/ where you expect /θ/.

It may be an accent feature, or a normal stage of speech development. Either way it tells you nothing about whether the child recognised the digraph, which is the thing being assessed.

Check that the child read th as one sound rather than two. That is what the reading lesson is testing.

Teacher note

Teach th as one sound and do not spend long on the voiced/unvoiced distinction for reading — children produce the correct one automatically in words they know, and the spelling gives them no way to choose in words they do not. The distinction matters for talking about sounds, not for decoding.

Accent notes

Indian English — th is commonly realised as a dental /t̪/ rather than /θ/ — thin sounds closer to tin with the tongue on the teeth. This is a standard feature of the accent and should not be corrected as a reading error.
General American and British English — Many young children substitute /f/ for /θ/ until around age six or seven. This is a speech development stage, not a decoding problem.

Learn these first

SH — sh — The most reliable digraph in English. One sound, one spelling, no exceptions a child will meet.

Related rules

Give your child a reading buddy.

To read with every step of the way.

The reading buddy that listens. Structured, personalised phonics for ages 4 to 10, in joyful minutes a day.

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