Joe Martin introduced the term featural notation to describe writing systems that include symbols to represent individual features rather than phonemes. He asserts that "alphabets have no symbols for anything smaller than a phoneme".
Examples of featural alphabets include the following:
Other alphabets may have limited featural elements. Many languages written in the Latin alphabet make use of additional letters with diacritics, which are sometimes considered separate letters. The Polish alphabet, for example, indicates a palatal articulation of some consonants with an acute accent. The Turkish alphabet uses the presence of one or two dots above a vowel to indicate that it is a front vowel. The Japanese kana syllabaries indicate voiced consonants with marks known as dakuten. The International Phonetic Alphabet (IPA) also has some featural elements, for example in the hooks and tails that are characteristic of implosives, ɓ ɗ ʄ ɠ ʛ, and retroflex consonants, ʈ ɖ ʂ ʐ ɳ ɻ ɽ ɭ. The IPA diacritics are also featural. The Fraser alphabet used for Lisu rotates the letters for the tenuis consonants P /p/, T /t/, F /ts/, C /tʃ/, and K /k/ 180° to indicate aspiration.