To begin, -*tion, -*sion, -*cion, and -*xion are not suffixes. Only -ion is a suffix. A suffix is a bound morpheme that attaches to the end of the stem of a word to form either a new word or a new form of the same word. A morpheme is the smallest meaningful linguistic unit of a language. A bound morpheme must attach to another morpheme to create a word.
I recently came across a tweet from Logic of English that stated <ti>, <si>, and <ci> all represent the /ʃ/ (sh) sound.
— Logic of English (@LogicofEnglish) June 21, 2019
This statement is unequivocally wrong. Many English words are spelled with <ti>, <si>, <ci>, and by extension <xi> that are not pronounced with a /ʃ/ sound. For example:
- tie, tin, tick, tile, time, patio, tight, tidbit, etiology
- sin, sir, sick, sink, sign, basic, siege, sirup, sister, sibling
- ciao, cion, cite, city, cider, circle, icing, recite, citrine, concise
- axis, exit, taxi, oxide, pixie, waxier, apraxia, lexicon, xiphoid, affixing
Logic of English offered a clarification, stating that the phonograms (graphemes) <ti>, <si>, <ci>, and <xi> never represent the /ʃ/ at the beginning of a word.
2/3 the sound /ʃ/ is represented by TI, SI, CI, or XI. These letter combinations function as phonograms in these words; they represent a sound visually.
— Logic of English (@LogicofEnglish) July 2, 2019
Although appearing together in written words, <ti>, <si>, <ci>, and <xi> are not graphemes. A grapheme is the smallest meaningful contrastive unit in a writing system. English graphemes are largely analogous to phonemes. A phoneme is the smallest unit of contrastive sound in a language. Graphemes cannot cross morphemic boundaries.
The <t>, <s>, <c>, and <x> belong to the base or stem of the word (with or without a replaceable <e>) in the following pairs:
When the <t>, <s>, <c>, or <x> (with or without a replaceable <e>) appears word-final in a base or stem, the pronunciation is /t/, /s/, /z/, /k/, or /ks/. The same rule applies to words that end in a suffix with a word-final <t>, <s>, <c>, or <x> (with or without a replaceable <e>) such as -ate. For example:
The word sum for <activate> is <Act + ive + ate>. The affixation of the -ion suffix results in the word sum <Act + ive + ate + ion>. The final sound in all the words that end in the -ate suffix is /t/. The affixation of the -ion suffix changes the /t/ to /ʃ/.
The -ion suffix forms abstract nouns from verbs. In Modern English, conversion is a productive word formation process. A grammatical form such as a noun can become a verb without changing form or pronunciation. A word such as <flirt> began as a noun. The verb form developed after the noun form. Thus, to affix the -ion suffix to <flirt> requires first the affixation of the -ate suffix to form a verb and then the affixation of the -ion suffix: <Flirt + ate + ion -> flirtation>.
For other words, the only verb forms ends in the -ate suffix:
Other word families have multiple forms with different meanings:
To summarize thus far, -*tion, -*sion, -*cion, and -*xion are not suffixes. Only -ion is a suffix. Graphemes cannot cross morphemic boundaries. <ti>, <si>, <ci>, and <xi> are not graphemes. <t>, <s>, <c>, or <x> belong with the base or stem. Only <i> belongs with the suffix.
Why does the affixation of the -ion suffix trigger a sound change in the final consonant of a base or stem?
- act /ækt/ ~ action /ˈækʃən/
- tense /tɛns/ ~ tension /ˈtɛnʃən/
- fuse /fjuz/ ~ fusion /ˈfjuʒən/
- coerce /koʊˈɝs/ ~ coercion /koʊˈɝʒən/ /koʊˈɝʃən/
- flex /flɛks/ ~ flexion /ˈflɛkʃən/
The first words with an -ion suffix end in a /t/, /s/, /z/, or /ks/ sound. The sound in the second word is /ʃ/ (sh) or /ʒ/ (zh).
The -ion suffix consists of the graphemes <i>, <o>, and <n>. The <o> represents the /ə/ sound. The <i> is a phonological marker that indicates the pronunciation of the preceding consonant, which is an example of morphophonology. Morphophonology examines the interaction between morphological and phonological or phonetic processes, focusing on the sound changes that take place in morphemes when combining to form words.
<i> as a phonological marker following <t>, <s>, <c>, and <x> is evident in words with suffixes other than -ion. For example:
- Fasc + i +a -> fascia /ˈfeɪʃjə/ /ˈfeɪʃi.ə/
- in + Ert + i + a -> inertia /ɪnˈɝ.ʃə/ /ɪˈnɝ.ʃə/
- Face + i + al -> facial /ˈfeɪʃəl/
- Space + i + al -> spacial /ˈspeɪʃəl/
- Spece + i + al -> special /ˈspɛʃəl/
- de + Fice + i + ent -> deficient /dəˈfɪʃənt/ /dɪˈfɪʃənt/
- Capt + i + ous -> captious /ˈkæpʃəs/
- de + Lice + i + ous -> delicious /dəˈlɪʃəs/ /diˈlɪʃəs/
- Tort + i + ous -> tortious /ˈtɔɹʃəs/
The <i> is a grapheme. The <i> is a connecting vowel. The <i> is a phonological marker that signals the pronunciation of the previous consonant. (Phonological markers are always graphemes.) The effect is especially apparent when comparing pairs of words in which the first word lacks the affixed connecting vowel and suffix:
Students deserve correct and complete information about the English writing system. -*tion, -*sion, -*cion, and -*xion are not suffixes, and <ti>, <si>, <ci>, and <xi> are not graphemes. As such, <ti>, <si>, <ci>, and <xi> do not represent a /ʃ/ (sh) or /ʒ/ (zh) sound. The <t>, <s>, <c>, or <x> is part of a base or stem. The <i> is a phonological marker.