In Taiwanese phonetics, aspiration is the strong burst of breath that accompanies the release of obstruents.
In Taiwanese Hokkien, the aspirated consonants are: [pʰ], [tʰ], [kʰ], [tɕʰ], [tsʰ]. In MTL, these are written: ph, th, kh, ch, zh. They are composed of the symbols for voiceless consonants (p, t, k, c, z) followed by the aspiration modifier letter h.
You may have already noticed that this is a bit different from English, which always aspirates p, t, and k when they occur at the beginning of words.
Why would we choose to use these letters different from English?
- POJ, the ancestor of MTL, also uses h to denote aspiration. This preserves b, (d), g, and j for voiced consonants.
- The convention of the apostrophe or "h" to denote aspiration is also found in romanizations of other Asian languages, such as McCune–Reischauer for Korean and ISO 11940 for Thai.
- The International Phonetic Alphabet (IPA) uses the aspiration modifier letter ⟨◌ʰ⟩ following symbols for voiceless consonants.
- In Japanese, the voiceless stops /p, t, k/ are slightly aspirated: less aspirated than English stops, but more so than Spanish.
- French, Dutch and Spanish don't even have aspirated consonants. So they use initial p, t, and k pretty much the same as in written Taiwanese.