/TH/ Sound Speech Therapy: Both TH Sounds & Error Fixes

TH is one of the last sounds a child masters, and one of the most misunderstood — because “TH” is not one sound at all. It is two different phonemes that happen to share a single mouth position, separated only by whether the voice is switched on. Say think, then say this: your tongue never moves, but one hums and one doesn’t. Understanding that single fact explains the errors children make with TH and tells you exactly how to fix each one.

This guide walks SLPs and parents through teaching both TH sounds — voiceless /θ/ (think, thumb) and voiced /ð/ (this, that) — and fixing the three common errors (th→f/v, th→t/d, th→s), with interdental placement, word lists by position, minimal pairs, developmental norms, and sample IEP goals.

This is written primarily for SLPs — clinical depth on error patterns, placement, word lists, minimal pairs, and IEP goals — with a clearly marked home-practice section for parents. Skip to the section you need.

The Two TH Sounds: Quiet vs Buzzy

English spells two entirely different consonants with the same two letters. Both are dental fricatives made at the same place, and they differ only in voicing:

• Voiceless /θ/ — the quiet TH. Vocal cords off, just airflow. Think, thumb, bath.
• Voiced /ð/ — the buzzy TH. Vocal cords on, adding vibration. This, that, feather, bathe.

“Quiet” versus “buzzy” is the child-friendly handle for that voicing contrast, and it recurs everywhere in this guide — in placement, in home practice, and in sequencing. It matters because both sounds use the same interdental placement: the tongue tip rests lightly between the teeth, and the only thing that changes is whether the voice is running. That shared placement is the wedge for the entire article. Teach the position once and you are two-thirds of the way to both sounds; the last third is a voicing switch.

Both TH sounds sit among the very last English consonants to develop, and both belong to Shriberg’s Late-8 group (/θ/, /ð/, /s/, /z/, /ʃ/, /ʒ/, /l/, /r/), the cluster of sounds children acquire last. That is why TH errors before age 6 or 7 are usually nothing to worry about, while the same errors later are legitimately worth targeting.

For a full single-sound reference on each phoneme, see the sound pages for the /θ/ sound and the /ð/ sound.

When Should a Child Say the TH Sounds?

Developmental norms decide whether TH is even an IEP concern. The values below come from Crowe & McLeod’s 2020 U.S. review — the current standard for American English consonant acquisition — with its cross-linguistic companion, McLeod & Crowe (2018).

Ages from Crowe & McLeod (2020); companion cross-linguistic data in McLeod & Crowe (2018).

Ages use the standard speech-pathology years;months format, not decimals. 3;6 means 3 years, 6 months old — not 3.6 years. 7;0 means 7 years, 0 months.

Read the mastery ages as “around age 6” for the voiced TH and “around age 7” for the voiceless TH, not as rigid thresholds. The table shows the whole-year mastery bands to stay consistent with the app, and “around” keeps the prose honest.

One number is worth stating plainly: the voiceless /θ/ has the latest 90% mastery age of all 24 English consonants in the norm set — later than /r/ (around age 6) and /s/ (around age 5). If a sound is going to still be developing in first grade, it is this one.

That reframes the IEP decision. A child at or past the ~7;0 (voiceless) or ~6;0 (voiced) mastery age who is still substituting or distorting TH, with an intelligibility or participation impact, is typically a reasonable target. Below those ages, TH errors are usually developmentally typical.

Two caveats keep this honest, as with any norms-based decision: being under age does not rule out an IEP (a highly unintelligible younger child may still need service), and being over age does not mandate one (a mild, fully intelligible residual TH may not meet eligibility).

For the full consonant timeline, see our speech sound milestones by age. And note one process that foreshadows the errors below: stopping of fricatives — replacing a sound like TH with a stop — is, by the app’s stopping-of-fricatives norm, normally suppressed by around 3;0, which is exactly why a lingering th→t/d is a flag. The error-patterns section below breaks that down.

Difference vs Disorder: When TH-Fronting Is an Accent

Before treating any TH error, rule out one thing no competing guide covers: dialect. Substituting f/v for TH — wiv for with, fink for think, bruvver for brother — is a recognized, systematic feature of several English varieties: African American Vernacular English (AAVE), many Southern U.S. varieties, and Cockney/Estuary English. In those dialects, th-fronting is a language difference, not a speech-sound disorder.

The clinical rule follows directly: a feature that is consistent with the child’s home and community dialect is not an error to remediate. Assess the child against their own linguistic community, not against General American. A Southern or AAVE-speaking child who fronts TH the way the adults around them do is producing their dialect correctly — there is nothing to fix, and treating it as a deficit is neither culturally responsive nor clinically appropriate.

This is also where the standard scope boundary belongs. Sound Safari is a clinical tool, not a medical device. It does not provide diagnoses or treatment recommendations. Screening and error-pattern features are informational, and clinical decisions should always be made by qualified professionals — including the judgment call of difference versus disorder.

Everything from here on addresses TH errors that are clinical targets — a true speech-sound disorder or a genuine unintelligibility impact — not dialect variation. Keeping that line clear is part of what makes a TH guide trustworthy.

The Three TH Error Patterns

Here is the clinical wedge most guides blur: there are three distinct TH errors, they belong to three different error classes, and each maps to a different minimal-pair fix. Sort the error first and therapy gets faster.

th→f/v is a straight substitution. The child reaches for an easier labiodental fricative (/f/, /v/) that needs far less precise tongue placement than the between-the-teeth TH. It is not the stopping process — nothing is being turned into a stop; one fricative is simply swapped for another that is easier to place.

th→t/d is stopping — a fricative replaced by a stop. Because stopping of fricatives is normally suppressed by around 3;0 (the app’s stopping-of-fricatives norm), a persistent th→t/d, especially past the TH mastery ages, is a clear phonological target rather than a stray articulation slip. The child keeps a familiar stop they already own and drops the harder fricative airflow.

th→s/z substitutes one fricative for another, and it matters clinically because it is the exact mirror image of the frontal (interdental) lisp. A child with a frontal lisp produces /s/ as TH — thun for sun. A child with a th→s error produces TH as /s/ — sink for think.

Same two phonemes confused, opposite directions — and the same S-vs-TH minimal-pair set treats both, just with the target flipped. The TH-vs-S section below covers that overlap.

The payoff: each error type maps one-to-one onto a named minimal-pair set — the three sections after the placement work. For the full stopping-and-fronting context, see our phonological processes guide.

How to Teach the TH Sounds: Interdental Placement

Because both TH sounds live at one shared position, you teach the placement once and split by voicing. Probe first, set the position, then toggle the voice.

Step 1 — Probe stimulability first

Before choosing anything, find out which TH the child can already approximate. Model both — the quiet /θ/ (think) and the buzzy /ð/ (this) — and listen for which one is closer. Many children find one easier than the other. Start with whichever is stimulable, because the placement is identical and, once one TH is stable, the other follows almost for free.

Step 2 — Set the shared interdental placement

The core target, shared by both phonemes: rest the tongue tip lightly between the top and bottom teeth, with only a small amount of tongue showing, then blow a steady, gentle airstream. That is the whole placement. The same posture produces /θ/ and /ð/ — this is the “differ only in voicing” trick made concrete, and it is why TH is efficient to teach once the child tolerates the tongue-between-teeth position.

Step 3 — Teach the voicing contrast with feedback

Now split the two sounds with tactile feedback:

• Quiet /θ/ (voiceless): vocal cords off. Check with a hand in front of the mouth to feel the moving air.
• Buzzy /ð/ (voiced): vocal cords on. Check with a hand on the throat to feel the vibration.

Add the mirror cue — have the child watch the tongue tip appear between the teeth, or “fog the mirror” with the airstream. Visible tongue plus felt voicing gives the child two feedback channels at once.

Step 4 — Get the second TH free by toggling voicing

Once one TH is stable, produce a sustained version of it and “turn the motor on or off” to reach the other. Shape from a held /θ/ and add voicing to land on /ð/; or start from /ð/ and drop the voice to reach /θ/. Because the placement never changes — hand on the throat for buzzy, hand at the mouth for quiet — the second sound is a voicing switch, not a new motor plan.

Step 5 — Watch for drift, then generalize

Two slips to catch early: the tongue retracting behind the teeth (which drifts toward t/d) and the tongue pulling back into a groove (which drifts toward s). Exaggerate the tongue between the teeth in a mirror until the correct posture is automatic. Then move through the practice hierarchy — the app’s six levels run Isolation → Syllable → Word → Phrase → Sentence → Story — which the word lists and IEP goals below operationalize. For the connected-speech rungs, there is real depth to draw on: Sound Safari carries 66 voiceless-/θ/ phrase prompts and 20 voiced-/ð/ phrase prompts at the Phrase level, so you are not inventing carrier phrases on the fly.

TH Word Lists by Position

Position-sorted word lists are the most bookmarkable asset in any sound guide — and because TH is two sounds, you need two lists, each split by position. Splitting voiced from voiceless and by position is exactly the gap most competitors leave.

Voiceless /θ/ ships 90 practice words — 30 initial, 30 medial, 30 final. Here is a working sample:

Voiced /ð/ ships 79 unique practice words — 30 initial, 30 medial, and 19 unique in the final position. Here is a working sample:

Most therapy starts word-initial (the easiest position to cue), then moves to final, then medial — where TH sits between two vowels and is easiest to collapse. That ties back to the placement ladder above and forward to the goal levels below.

Sound Safari generates these position-sorted lists for you — 30 words per position for the voiceless /θ/, and the voiced /ð/ lists too — so you are picking from a set rather than building one by hand.

TH vs F Minimal Pairs: Fixing TH-Fronting

Minimal pairs are the standard evidence-based fix for the th→f/v substitution. Caroline Bowen’s point holds here as it does for other sounds: as few as 3–5 well-chosen minimal pairs can drive generalization to untreated words (Elbert et al., 1991, as Bowen cites it), so a small, sharp set does real work.

Sound Safari’s curated TH-vs-F set carries four pairs:

The app also ships an illustrated f-th set of 5 pairs so you can run the contrast without printing worksheets. (Note: think/fink was deliberately removed from the database — fink is not a word most children know, so it makes a weak contrast.)

Why the contrast works: hearing thin versus fin makes the missing interdental tongue placement meaningful. The child gets a communicative reason to put the tongue between the teeth, because the two words mean different things — contrast for repair. Browse the full library of minimal pairs to see the contrasts in one place.

TH vs S Minimal Pairs: The Frontal-Lisp Overlap

This set targets the th→s/z error, and it is the same set the app files under fronting / “frontal lisp.” Sound Safari ships 10 illustrated s-th pairs:

Here is the relationship worth keeping straight, first named in the error-patterns section: the same S-vs-TH contrast treats both directions. For a th→s error the target word is the TH one (think, not sink). For a frontal lisp — where /s/ comes out as TH — the target word is the /s/ one (sink, not think). You flip which word is the target; the deck stays the same. That is the direct clinical bridge to the /s/ work in our /s/ sound therapy guide, the companion for the frontal (and lateral) lisp side.

TH vs T and TH vs D Minimal Pairs: Fixing Stopping

The th→t/d stopping pattern (a fricative replaced by a stop) gets two voicing-matched sets, because a voiceless TH stops to /t/ and a voiced TH stops to /d/. In Sound Safari the TH-vs-T set carries 11 illustrated pairs (categorized “stopping”) and the TH-vs-D set carries 9 pairs.

Why the contrast works: it forces the child to add back the fricative airflow that stopping drops. Tin versus thin makes the difference between a stop and a between-the-teeth fricative meaningful; day versus they does the same on the voiced side. The two sets exist because the target must be voicing-matched to the stop it replaces.

Because th→t/d is a phonological process rather than a single-sound distortion, it often patterns with other stopping errors across several fricatives — which is why it gets its own phonology goal below, and why the app can flag the pattern from session scoring.

Sample IEP Goals for the TH Sounds

Once TH is confirmed as a target — gated by the mastery ages above, with an intelligibility impact — you need measurable goals. Sound Safari’s goal bank ships 22 built-in templates across 8 categories (articulation, phonology, fluency, voice, receptive language, expressive language, pragmatics, and phonological awareness), all defaulting to an 80% accuracy criterion across 3 consecutive sessions. (The sample goals below say “20 trials in 3 of 4 consecutive sessions” — the “20 trials” and “3 of 4” are common clinician conventions layered on the app’s underlying 3-consecutive-session default, not app values.)

For a straightforward TH substitution (th→f or th→s), the child is producing TH correctly, so you use the articulation “Sound in Word Position” template — suggested baseline 0–40%, 80% accuracy, 12–36 weeks:

Goal 1 (voiceless /θ/, word position): Given a verbal model and tactile cues, [Student] will produce the voiceless /θ/ in the initial position of single-syllable words (e.g., think, thumb, three) with 80% accuracy across 20 trials in 3 of 4 consecutive sessions by the end of the IEP year. Suggested baseline: 0–40%. Timeframe: 12–36 weeks.

Goal 2 (voiced /ð/, word position): Given a verbal model and tactile cues, [Student] will produce the voiced /ð/ in the initial position of single-syllable words (e.g., this, that, they) with 80% accuracy across 20 trials in 3 of 4 consecutive sessions by the end of the IEP year. Suggested baseline: 0–40%. Timeframe: 12–36 weeks.

The th→t/d stopping pattern is different. Because it usually spans several fricatives, it has its own phonology template — “Stopping” — with suggested baseline 0–30%, 80% accuracy, 20–40 weeks:

Goal 3 (stopping, phonology): [Student] will eliminate the process of stopping by producing fricatives — including /θ/ and /ð/ — correctly with 80% accuracy across 3 consecutive sessions by the end of the IEP year. The app supplies this template’s goal text, 80% criterion, suggested baseline (0–30%), and timeframe (20–40 weeks).

That articulation-versus-phonology split is the important distinction: th→f and th→s go through the articulation templates (the child just needs to produce TH), while th→t/d gets the phonology template because it is a pattern, not one sound. A sentence-level goal is a common next step you write yourself — the app has no dedicated sentence-level template, so the baseline and timeframe below are illustrative planning conventions, not app values:

Goal 4 (sentence level — illustrative): Given a sentence frame and picture cues, [Student] will produce both TH sounds in all word positions within structured sentences with 80% accuracy across 20 trials in 3 of 4 consecutive sessions by the end of the IEP year. Suggested baseline: 35–55%. Illustrative timeframe: 16–24 weeks.

The app operationalizes these goals with two scaffolds. Trials are scored Correct / Approximate / Incorrect — Approximate is an opt-in setting, so the default is simply Correct/Incorrect. And there are four prompting levels: Maximum (Picture + Word + Model), Moderate (Picture + Word), Minimal (Word Only), and Independent (Picture Only). Fading from Maximum to Independent is how the goal’s cue condition tightens over the year.

Every goal here is a starting point, not a substitute for clinical judgment, baseline data, or your district’s conventions. For the full copy-paste set, including a dedicated TH progression, see our IEP goal templates. In Sound Safari, session scoring links straight to the goals you have written, so the probe data behind each one stays current without manual re-entry.

Home Practice for Parents

This section is for parents and caregivers — no clinical background needed. (An “SLP” is a speech-language pathologist, the professional who treats speech sounds.)

First, reassurance. TH is the latest sound most children master, so a 5- or 6-year-old still saying “fumb” for thumb or “dis” for this is often right on track. It is worth checking with an SLP if your child is clearly past around age 7 and still swapping the quiet think TH, past around age 6 for the buzzy this TH, or if unfamiliar listeners have trouble understanding them. And one gentle caveat: if your family’s own accent uses “f” for “th,” that may simply be your dialect, not an error — more on that in the difference-versus-disorder section above.

A few simple things help at home:

1. Mirror game. Have your child rest the tongue tip peeking between the teeth and blow air. Seeing the tongue makes it click.
2. Quiet vs buzzy. Hand in front of the mouth for the quiet TH — the think sound (feel the air); hand on the throat for the buzzy TH — the this sound (feel the buzz). Same tongue, different switch.
3. Model, don’t correct. If your child says “wiv” for with, don’t demand a redo — just say the word correctly two or three times in natural conversation. Hearing the right version matters more than drilling it.
4. Short and frequent. Three to five minutes a few times a week beats one long session. TH is a motor skill, and little-and-often builds it fastest.
5. Play with picture pairs. Line up pictures like thumb/fun and thin/tin and let your child hear — and see — that they are different words.

If you want a little more structure, Sound Safari’s parent view walks through TH practice with pictures right in your web browser — no app to download. Your child’s practice data stays on your device and your private iCloud; no third party ever receives your child’s practice or clinical data — no ads, no behavioral tracking, no data brokers. Account sign-in and subscriptions are handled by standard providers. See what parents get.

From Practice to Progress: Tracking TH Therapy

The hardest part of TH therapy is not picking a technique — it is knowing which of the three errors a child is actually making, session to session. Sound Safari flags the TH error pattern — th-fronting, stopping, or th→s — automatically from session scoring, so you know at a glance whether to run the TH-vs-F, TH-vs-T/D, or TH-vs-S set. That closes the loop this whole guide is built around: sort the error, then match the fix.

The detection sits inside a single workflow — practice, screen, document, and share, all in one app. The built-in articulation screener covers 24 sounds across the initial, medial, and final word positions, and it samples both TH sounds both ways — voiceless via thumb / birthday / bath, voiced via this / feather / bathe. It checks each against developmental norms, replacing the $200+ you would otherwise spend on separate assessment tools.

And it is the only articulation app with auto-generated SOAP notes — session data flows into the standard four-section clinical structure (Subjective, Objective, Assessment, Plan), so the documentation is largely written by the time the session ends. For the screening side, see our articulation screening checklist; for the documentation side, see writing SOAP notes in speech therapy.

Sound Safari is a clinical tool, not a medical device. It does not provide diagnoses or treatment recommendations. The screener is informational — clinical decisions should always be made by qualified professionals. To put the full loop to work, Sound Safari for professionals was built for exactly this.

Frequently Asked Questions

Closing

Teach TH by understanding what it actually is — two sounds sharing one interdental placement, the quiet /θ/ and the buzzy /ð/, separated only by voicing — and the errors stop being confusing. Match the fix to the error: th→f with TH-vs-F pairs, th→t/d with TH-vs-T and TH-vs-D pairs, th→s with TH-vs-S pairs. Gate the decision to treat on the mastery ages — around 7 for the voiceless TH, around 6 for the voiced TH — and remember that dialectal th-fronting is a difference, not a disorder.

The goals and templates here are starting points, not a replacement for your clinical judgment and baseline data. Use them as scaffolding and adjust to the student in front of you.

If you want structured TH practice with position-sorted word lists for both sounds, all three labeled minimal-pair sets, automatic error-pattern detection, and progress an SLP can review, Sound Safari was built for this workflow. 14-day free trial. No credit card required. Cancel anytime through Apple.