Spelling changes vs. Stem changes
The distinction between these two types of changes in conjugated verbs has not been specifically made clear in any of the grammar texts I've used. (including the grammar resources on this site.) I believe however, that I have finally realized what the difference is. It appears to be: "spelling changes" refer only to those changes of the spelling and pronunciation of the endings (the inflections) of those certain persons and tenses of the verbs which are subject to these changes. Stem changing verbs are those in which the spelling of the stem is changed in some tenses and persons and some verbs are subject to both types of changes.
If this is elementary and entirely obvious, I regret that I've been so incompetent for so long, but because both "spelling changing verbs" and "stem changing verbs" require spelling changes from the way regular verbs are conjugated, I have not understood why the distinction was made. I hope I have it now. If not, your better informed counsel will be appreciated.
Also, I'm not clear about what it is that makes a verb "irregular." I read in some places that "these are not technically "irregular." Yet, they do have at least the spelling changes of the inflections. If the only change(s) is/are in the ending(s), are the verbs "irregular"?
4 Answers
Let me try to explain:
Give a computer program very basic rules, like if a verb ends in -ar, then drop that ending and use -o, -as, -a, -amos, -áis, -an for the present. You get "amo", amas", ama"... So far, so good. This pattern will work well with thousands of verbs.
Now give the poor program the verb "empezar", which changes to "empiezo", "empiezas"... The program will follow the instructions, and will get "empezo", "empezas"... which is wrong. This is an irregular verb.
Bear in mind that native speakers have always used conjugations even if they could not read or write, so the verb patterns must be based on sounds, which is what we all share as natives. A verb like "amar" should always sound 'am...' whatever, if it is regular, but "empez" does not always sound like 'empez...' whatever, because it is irregular.
Now let's take again the verb "vencer", which is regular. In present subjunctive you should normally add the sounds -a, -as, -a, -amos, -áis, -an, if it is regular. Also, the root should always sound the same. Ok, let's ask a native how to say this verb in present subjunctive. The native will sound like the root... plus the relevant endings. Great! Let's write it down:
venca, vencas, venca...
Hold on! That sounds like "venk", not like the root of "vencer". That's not how it is supposed to sound! Why? Because the letter c sounds different between e (vencer) and a (vencar), so by keeping the original spelling, we've ruined the sound and we have made it unrecognisable to natives. The solution? Change the spelling to maintain the sound regular: "venza", "venzas"... Now it sounds regular. This is a regular verb with regular spelling changes applied to maintain the correct sound. Now we just need to tell the computer program that whenever the verb ends in -zar, it must always modify the z before e or i. Even if you give the program a newly created verb, it will get the perfect regular pattern every time.
So what about irregular verbs? There is no simple rule that tells you how are they going to behave. They may add sounds, change sounds, or change altogether, and nothing can help your computer program decide with 100% certainty how to correct for them, unless you give your program an exhaustive list of irregular verbs, but then, if a new one is born, it will get it wrong.
Does it make sense?
It would have been much better if you had given examples of a spelling change contrasted to a stem change with a few example verbs.
Would the Go verbs be a spelling change or a stem change by whatever your criteria is?
poner-pongo (spelling change)
poder-puedo (stem change)
Verbs can be regular in some tenses and irregular in other tenses so the term irregular verb is not precise. It usually just refers to verbs that are not regular (have predictable patterns of conjugation.)
Another verb I ran across that is totally irregular is caber and the the text of what made this verb irregular was the following which I do not understand at all...
It is not "totally" irregular. The present indicative forms are all regular except "quepo". Latin verbs were not exactly regular, and although many became regular in time, commonly used ones maintained all sort of irregularities, because you were corrected by your parents as soon as you opened your mouth. Other irregularities were created in the process too, but that's another story.
"Caber" comes from the Latin verb "capere", which in present tense was "capio", "capis", "capit"... The Latin perfect was "cepi", "cepisti"... (pronounced as "kepi", "kepisti"...). The infinitive was "capere" (drop the final "e", weaken the "p" to a "b", and you have "caber), and the future infinitive was capturus (guess what word it is now!) A lot of the original forms sounded like kep..., which is why nowadays is written as "quep".
Verbs like ir and ser are considered totally irregular since when you drop the "ir" and the "er" what do you have? These 2 verbs are all over the place in their conjugations and I would say you would have to memorize. Another verb I ran across that is totally irregular is caber and the the text of what made this verb irregular was the following which I do not understand at all...
"SÍNCOPA - Loss of the protonic vocal: e"
It would be easier if someone listed just the "totally" irregular verbs which I have read somewhere is suppose to be around 26.
