Why Spanish Speakers Struggle with the English 'TH' — And How to Fix It

If you grew up speaking Spanish, the English "TH" sound is one of the trickiest obstacles on the road to fluent pronunciation. It doesn't exist in Spanish phonology, which means your brain has never had to produce it before — and your mouth needs to learn completely new muscle memory.

The good news: this is one of the most teachable sounds in English. Give it focused practice and you'll master it faster than you think.

Why There's No Spanish "TH"

Spanish has 27 phonemes. English has 44. Several English sounds don't exist in Spanish — and the "TH" family is at the top of that list. When Spanish learners encounter words like think, the, those, or this, the brain searches for the closest native sound and finds:

• T (like the Spanish t in toro) — so "think" becomes "tink"
• D (like the Spanish d in dedo) — so "the" becomes "de"
• S — so "thing" becomes "sing"
• F — so "three" becomes "free" (very common in the Caribbean)

None of these substitutions is correct, and native speakers often struggle to understand words when these substitutions are made — especially in fast conversation.

Meet the Two TH Sounds

English actually has two distinct TH sounds that share the same spelling. This trips up even advanced learners.

1. The Voiceless TH — /θ/ ("theta")

Symbol: /θ/
Voiced? No — your vocal cords are NOT vibrating.
Examples: think, three, tooth, bath, month, thousand, author

2. The Voiced TH — /ð/ ("eth")

Symbol: /ð/
Voiced? Yes — your vocal cords ARE vibrating.
Examples: the, this, that, those, them, breathe, father, smooth

The difference between /θ/ and /ð/ is the same difference between /s/ and /z/, or /f/ and /v/ — air escaping through the same mouth position, but with or without vocal cord vibration.

How to Produce the Sounds: Step-by-Step

Voiceless /θ/ (think, three)

1. Open your mouth slightly. Relax your jaw.
2. Place the tip of your tongue lightly against the back of your upper front teeth — or just barely out between your teeth.
3. Blow air through the small gap between your tongue and teeth.
4. Do NOT vibrate your vocal cords. The sound is pure air.
5. Test it: Put your hand in front of your mouth. You should feel a gentle puff of warm air.

(Listen in Voza for the audio version)

Quick test: Say the letter "S" — now slide your tongue forward until it touches the back of your upper teeth. That forward, airy position is /θ/.

Voiced /ð/ (the, this, that)

The position is identical to /θ/, but now add voice:

1. Same tongue placement — tip touching or peeking between teeth.
2. Start vibrating your vocal cords before air escapes.
3. The sound should feel like a buzzing vibration.

Quick test: Put two fingers gently on your throat (Adam's apple area). For /ð/, you should feel vibration. For /θ/, nothing.

(Listen in Voza for the audio version)

Minimal Pairs Practice

Minimal pairs are pairs of words that differ by only one sound. These are gold for training your ear and mouth simultaneously.

/θ/ vs. /s/

| /θ/ (TH) | /s/ (S) | |-----------|---------| | think | sink | | three | free → Actually /θ/ vs /f/ too | | thank | sank | | path | pass | | math | mass | | month | once (roughly) |

/θ/ vs. /t/

| /θ/ (TH) | /t/ (T) | |-----------|---------| | think | tink (not a word — that's the error!) | | three | tree | | thick | tick | | thread | tread | | bath | bat | | tooth | toot |

/ð/ vs. /d/

| /ð/ (TH) | /d/ (D) | |-----------|---------| | them | Dem (name) | | those | doze | | though | dough | | breathe | breed | | father | fodder| | other | udder |

Practice Sentences: /θ/

Say these out loud, slowly at first, then at natural speed. (Listen in Voza for audio pacing)

1. "I think three thousand things a day."
2. "The author wrote about birth and death."
3. "On Thursday, I go to the theater."
4. "Thank you for your thoughtful gift."
5. "The theme of the thesis is thoroughness."
6. "She put her tooth in the cloth."

Practice Sentences: /ð/

1. "The cat sat on the mat, not the other one."
2. "This is their house, not that one."
3. "They said they would go together."
4. "I'd rather stay here than go there."
5. "My father and mother live in the south."
6. "Whether it rains or not, we'll be there."

The Tricky Cases: When to Use /θ/ vs. /ð/

There's no 100% rule, but patterns exist:

Usually /θ/ (voiceless):

• Words starting with th + consonant cluster: three, throw, through, throne
• Content words (nouns, adjectives, verbs): think, thought, tooth, truth, author, birthday
• Words ending in -th: bath, cloth, math, month, health, breath (noun)

Usually /ð/ (voiced):

• Function words (articles, pronouns, conjunctions): the, this, that, these, those, them, they, their, then, though, although, whether
• Words ending in -the or -the + s: breathe, soothe, loathe, clothe

The Fastest Way to Build Muscle Memory

Method 1: Tongue anchor practice

Hold a pencil lightly between your front teeth (not biting, just barely touching). Try to speak sentences with TH words. This forces your tongue forward into correct position.

Method 2: "S-slide" drill

Start saying /s/, then slowly slide your tongue tip forward until it touches the back of your upper teeth. That end position — with air still flowing — is /θ/.

Method 3: Shadow pronunciation with Voza

Shadowing means listening to native speech and repeating immediately, matching rhythm and sounds. Voza's AI coach listens in real time and flags TH errors specifically, so you know exactly when you're substituting /t/ or /d/.

Check your current pronunciation score and see how you rank on the TH categories.

Common Errors By Native Language Background

Mexican and Central American Spanish speakers

Most common substitution: T for /θ/ and D for /ð/.
"I tink" instead of "I think."
Focus on: voiceless TH words — think, thought, three, thank you.

Caribbean Spanish speakers (Cuba, Puerto Rico, Dominican Republic, Venezuela)

Common substitution: F for /θ/ in certain positions.
"free" instead of "three."
Focus on: voiceless TH, especially at the start of words.

Rioplatense Spanish speakers (Argentina, Uruguay)

Common substitution: similar to Mexico; occasionally S in some dialects.
Strong interference from the /ʒ/ (like English "measure") — keep that separate.

One More Thing: TH Is Worth the Effort

Why spend time on TH specifically? Because it shows up in the most common words in English:

• The — the single most frequent word in written English
• This, that, these, those, they, them, their
• Think, thought, three, thank, though, with, other, another, either, whether

Mispronouncing these words affects every sentence you speak. Fixing TH pronunciation has a disproportionate positive impact on how fluent you sound to native speakers.

Quick Reference Card

| Sound | IPA | Position | Example words | Common Spanish error | |-------|-----|---------|--------------|---------------------| | Voiceless TH | /θ/ | Tongue tip touches back of upper teeth; no voice | think, three, tooth, bath | /t/ or /s/ or /f/ | | Voiced TH | /ð/ | Same position; vocal cords vibrate | the, this, that, they | /d/ or /z/ |

Next Steps

1. Record yourself saying the practice sentences above.
2. Listen back critically — are you producing air flow between tongue and teeth, or are you hitting a hard stop (/t/ or /d/)?
3. Use Voza's pronunciation trainer for daily 5-minute TH drills with real-time AI feedback.
4. Check out our related guide: How to Think in English Without Translating — because good pronunciation is only part of fluency.

The /θ/ and /ð/ sounds are difficult because they're new, not because they're complex. With 10 minutes of deliberate practice per day, most Spanish speakers notice a clear improvement within two to three weeks. Start today.