f/f/
Lift your bottom lip to touch the very bottom of your top front teeth. Blow air through this contact point without voicing.
How to pronounce photosynthesis in American English
foh·tuh·SIHN·thuh·suhs
Start here
Americans pronounce photosynthesis as foh-tuh-SIHN-thuh-suhs (/ˌfoʊɾəˈsɪnθəsɪs/). In "photosynthesis", the "t" between vowels sounds like a quick "d" — the tongue briefly taps the ridge behind the upper teeth. This is called the Flap T, and it's why Americans sound more relaxed than the textbook. It comes out as FOH·tuh·SIHN·thuh·suhs. Stress falls on the third syllable — keep everything else short and quick. You'll hear it in sentences like "Photosynthesis is the process used by plants to convert light into energy".
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Sound by sound
Every sound in "photosynthesis".
5 syllables, 12 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
oh/oʊ/
Start with your mouth slightly open, then close your jaw slightly as your lips round. Shift your tongue back slightly, then stretch the back up.
t/t/
FlapQuickly bounce the front of your tongue against the roof of your mouth. Don't stop the airflow — just a quick tap.
uh/ʌ/
Relax your lips, jaw, and tongue completely. Drop your jaw slightly and keep the tongue neutral.
s/s/
Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.
ih/ɪ/
Drop your jaw slightly with relaxed lips. Touch the tongue tip behind the bottom front teeth and arch the top-front toward the roof.
n/n/
Touch the tip or front edge of your tongue to the roof of your mouth behind your teeth. Air flows through your nose.
th/θ/
Place the very tip of your tongue slightly between your teeth. Blow air gently around it without voicing.
uh/ʌ/
Relax your lips, jaw, and tongue completely. Drop your jaw slightly and keep the tongue neutral.
s/s/
Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.
uh/ʌ/
Relax your lips, jaw, and tongue completely. Drop your jaw slightly and keep the tongue neutral.
s/s/
Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.
In real conversation
Hear "photosynthesis" in the wild.
Click any sentence to see the full breakdown — every link, every reduction, every flap-T.
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Watch out
Common pronunciation mistakes in American English.
The textbook way isn't wrong — it's just not how anyone actually says it.
01
Saying a hard "T" in the middle.
In "photosynthesis", the "t" between vowels sounds like a quick "d" — the tongue briefly taps the ridge behind the upper teeth. /t/ or /d/ becomes a quick tap [ɾ] — sounds like a soft D. The tongue briefly taps the ridge behind the upper teeth.
foh-tuh-SIHN-thuh-suhs→FOH·tuh·SIHN·thuh·suhs
02
Stressing the wrong syllable.
Stress falls on the third syllable, not the others. Stretch SIHN — keep everything else short and quick.
FOH·TUH·sihn·THUH·SUHS→FOH·tuh·SIHN·thuh·suhs
03
Pronouncing the unstressed syllable too fully.
Don't pronounce the first syllable too fully. The unstressed syllable reduces to a schwa — the lazy "uh" sound — in casual speech.
foh·TUH·SIHN·thuh·suhs→FOH·tuh·SIHN·thuh·suhs
Questions
Questions people ask about this.
How is "photosynthesis" stressed in American English?
Stress falls on the third syllable — say "SIHN" with a longer, fuller vowel and keep every other syllable short and quick. The respell "foh-tuh-SIHN-thuh-suhs" marks the stressed syllable in capitals so the rhythm is easy to read at a glance.
Why doesn't the T sound like a T in "photosynthesis"?
In American English, when /t/ sits between two vowels with the second one unstressed, it turns into a quick D-like flap. So "photosynthesis" sounds closer to "foh-tuh-SIHN-thuh-suhs" than to a crisp-T pronunciation. This is the flap-T rule, one of the most distinctive sounds of casual American speech.
Why does the second syllable in "photosynthesis" reduce to "uh"?
Unstressed syllables in American English collapse toward a schwa — a lazy, neutral "uh" sound. The full vowel is what textbooks teach, but in actual American speech every unstressed vowel reduces. The respell "foh-tuh-SIHN-thuh-suhs" shows the reduced form so you can hear the casual rhythm directly.
Is the American pronunciation of "photosynthesis" different from British English?
American English uses different vowel shapes, a relaxed retroflex R, and connected-speech tricks like flap-T and glottal-stop T that British Received Pronunciation generally avoids. The respell "foh-tuh-SIHN-thuh-suhs" reflects the casual American form; British dictionaries typically print a citation form with crisper consonants and different vowel choices.
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