A consonant sound is a speech sound caused by a constriction or closure at some point along the vocal tract. Every syllable is understood to also contain a vowel sound but does not have to include a consonant.
Most English dialects have 24 consonants (counting semivowels /j/ and /w/). Many consonants are normally spelled with one letter or digraph, but several of them have an inconsistent spelling. For example /ʃ/ can unambiguously be spelled as "sh", but there are several other spellings such as "ti" in nation or "ce" in ocean, and ch in chef.
The following letters or digraphs unambiguously spell consonant phonemes: b, ch, d, g, h, j, k, l, m, n, p, r, sh, t, v, w, y, z.
The following phonemes can't be spelled unambiguously:
- /θ/ as in thank, because "th" can be either /θ/ or /ð/.
- /ð/ as in then, for the same reason
- /ŋ/ as in thing, because "ng" can represent /ŋ/ or /ŋg/ (as in "finger")
- /ʒ/ as in pleasure (however "zh" is sometimes used).