A phoneme is the smallest unit of sound that distinguishes one word from another in a language. English speakers hear pit and bit as different words because they begin with two different phonemes — /p/ and /b/. Same vowel, same final consonant; one tiny initial difference and the meaning flips.
The International Phonetic Alphabet (IPA) is the linguists' one-symbol-per-sound notation. The English letter c can be /k/ in cat or /s/ in ceiling or even /tʃ/ in cello — IPA cuts through that mess. Below is a reference keyed to English examples. Use it whenever a puzzle asks you to transcribe what you hear, or to read off a phoneme map you've drawn for an unknown script.
Slashes vs. brackets. Linguists write /p/
with slashes when treating a sound as a phoneme of a language, and
[p] with square brackets for the actual articulated
sound. For the puzzles on this site, the slash form is what you'll
use. Audio. For real recordings, the ILC's
IPA chart page
plays every symbol on click.
Vowels
Vowels are open sounds — the air flows through without obstruction. They differ in where in the mouth the tongue is (front to back) and how open the mouth is (close to open). The English vowel inventory below is roughly the General American set; British English distinguishes a few more.
Stops
Air is fully blocked for an instant, then released. Each pair below contrasts voiceless (vocal cords still) and voiced (vocal cords vibrating). Put your fingers on your throat as you say pat and bat — you'll feel the difference.
Fricatives
Air is squeezed through a narrow gap, producing turbulent friction. Again paired voiceless / voiced.
Affricates · Nasals · Approximants
Affricates are a stop immediately followed by a fricative, treated as one phoneme. Nasals route the air through the nose. Approximants just narrow the airway without friction — vowel-like consonants.
Symbols you'll meet in the puzzles
English uses only a fraction of the world's phonemes. The olympiad problems on this site reach into Australian, Papuan, Native American, Caucasian and other inventories — here's a working set of the symbols beyond the English set, with the closest English anchor we can give.
Diacritics & marks above the letter
Small marks decorate base symbols to indicate length, nasalisation, tone, and other modifications.
A working reference for the puzzles, not a comprehensive IPA chart. For the full thing, see Wikipedia's International Phonetic Alphabet page or the ILC IPA chart (which plays audio per symbol). Examples here lean on General American English; British, Australian, Indian and other varieties differ in a few vowels. Back to all puzzles.