There is a long-held belief that the <-tion> / <-sion> letter strings at the ends of words are in fact suffixes. This belief is wrong.
Consider the following examples:
action, option, construction, injection, vision, fusion, explosion, expansion
Now, let’s analyze them according to both the bogus phonics syllable division rules and the actual morphemic structure of the words:
First phonics: analysis, (Vowel or Consonant) [type of syllable] *I have been informed that a “final stable syllable” is a thing in phonics. That understanding is completely uninformed by actual linguistics, but this is a “phonics analysis” so to be consistent, I edited the post to reflect that.
ac/ tion (VC, CVVC) [closed, final stable]
op/ tion (VC, CVVC) [closed, final stable]
con/ struc/ tion (CVC, CCCVC, CVVC) [closed, closed, final stable]
in/ jec/ tion (VC, CVC, CVVC) [closed, closed, final stable]
vi/ sion (CV, CVVC) [open, final stable]
fu/ sion (CV, CVVC) [open, final stable]
ex/ plo/ sion (VC, CCV, CVVC) [closed, open, final stable]
ex/ pan/ sion (VC, CVC, CVVC) [closed, closed, final stable]
Now, morphology: lexical algorithm, [element]
act + ion -> action [prefix + base]
opt + ion -> option [prefix + base]
con + struct + ion -> construction [prefix + base + suffix]
in + ject + ion -> injection [prefix + base + suffix]
vise/ + ion -> vision [base + suffix]
fuse/ + ion -> fusion [base + suffix}
ex + plose/ + ion-> explosion [prefix + base + suffix]
ex + panse/ + ion -> expansion [prefix + base + suffix]
While the patterns of syllable division can account for a certain consistency within one individual word, take a look at the generative nature of the lexical algorithm:
ac/ tion act + ion -> action
ac/ tions act + ion + s -> actions
act/ ing act + ing -> acting
act/ ed act + ed -> acted
In only two of the four analyses from phonics does the base appear, making a solid 50%. <ac> and <act> are not in fact allomorphs, so those first two analyses are inaccurate.
As for productivity:
First, in action, the derivational suffix <-ion> reliably comes from Latin or French and creates nouns from verbs. This is just as reliable as phonics, and isn’t linguistic mythology.
Second, when adding the plural <-s> suffix to create actions, a six-year-old can determine that we are talking about more than one action. The <-s> suffix doesn’t always create plurals though. He acts in the play represents an example where the <-s> marks the third person singular present tense verb. Certainly not going to make this distinction in phonics.
Third, the <-ing> derivational suffix is common in English: acting, playing, driving, swimming, jumping, running. This suffix also has different functions when it surfaces in words in English.
Fourth, the <-ed> inflectional suffix also has multiple functions. As a teacher, I could create several sentences using acted to spark a discussion: He acted in the play last night. He had acted up, so wasn‘t allowed to go to the play. In the first sentence, acted is the simple past tense form, whereas in the second sentence, acted is the past participle form. The differences between forms and functions and the ability to construct sentences can only be discussed if the word is analyzed using one type of criteria from above, namely the lexical algorithm.
I don’t expect my students to know all of the grammar. They are nine and ten. My own knowledge of this stuff is hazy at best. But, the structures exist whether I understand them or not. They aren’t created on false constructs.
In contrast, when analyzing words, phonics tends to simply discuss the word at hand. In other words, it isn’t generative:
Actions is disyllabic so the analysis would be ac/ tions. Rather than talk about the function of <-tions>, because there isn’t one, my phonics manual tells me to skip straight to the pronunciation: /ʃəns/. Not a whole lot of meaning there. In fact, none. And not anywhere to go with a discussion either. The word actions could be discussed, but not the morphemes. <ac> is not a morpheme, and <tions> is neither inflectional nor derivational.
Maybe even more troubling is that I have yet to see a word in English that has a <-tion> or <-sion> suffix.
Only through accurate morphological analysis of words like action, actions, acting and acted, rather than obscuring the morphology in favor of pronunciation, can we see that the <-tion> and <-sion> letter strings are not in fact suffixes.