Prontamente

Prontamente
 

So I started reading up on how to form adverbs, and the process seems pretty straightforward.
Masculine form -> Feminine form -> Add -mente

In a different chapter on the same site, I found the phrases

And Lo behold, I thought too myself, something is not regular here.
Both quickly and slowly are adverbs (right?), but for some reason pronto is not in the common adverb form in the sentence.
I looked at the sites list of common irregular adverbs, but pronto was not among them. After a google search I found a site that discussed rapido and rapidamente, but the members were basically saying "It sounds wrong and right at the same time. Not commonly used but we don't think it's wrong either".

So what gives? If it was a common exception, I thought they'd say so at the other forum but it wasn't mentioned.


Thanks in advance,
Jimmy

Many adjectives are also adverbs, and many more are used as adverbs in colloquial speech (as "good" in English, "I'm good!"). A lot of adjectives are cast into adverbial phrases by adding "de".

Hable lentamente (adv) = Hable despacio (adv) = Hable más lento (adj>adv)

pronto (soon, not quickly) ---> Vuelvan pronto
rápido (adj.: fast) ---> (adv.: quicly) ---> Ve rápido/rápidamente (Go quickly)

I can't offer systematic rules, as there are changes of nuances, even meanings -as adjective use to have more than one-, and there are changes of sociolects. For example:

Está pronto a salir (he's leaving any minute) --->formal, maybe dated, "cloak and dagger".
Vuelve pronto (come back soon) ---> standard language
Vuelve prontamente (come back quickly) ---> formal, a bit of a Barroque.

Hable lentamente (speak slowly) ---> standard language, a bit formal
Hable despacio (speak slowly) ---> standard language
Habla lento (speak slowly) ---> pretty low level, tolerated in some regions

What you are calling an irregular adverb isn't. Not all adverbs end in -mente. The same holds true in English. The English word 'soon', which is one of the translations of pronto, doesn't end in -ly. There are many adverbs that fit in this category, in both languages.

Spanish admits both pronto and prontamente, although I've never heard the latter used.

In English, both quick and quickly are used as adverbs.
Both slowly and slow can be used as adverbs. By the same token, both lentamente and lento are adverbs in Spanish.

For giggles, here's a non-exhaustive list of adverbs that don't end in -ly. Find the Spanish translations. ;)
almost, well, always, less, more, too, often, never, not, very, even, far, fast, tomorrow, yesterday, today, quite, elsewhere, likewise, sometimes

That, although nowadays increasingly widely used is bad English. Good is an adjective of quality, well is the correct adjective of health. I believe it to be a newish Americanism, which regretably has crossed the Atlantic.

Please avoid the temptation to patronise me with "Language changes", the eternal excuse of those who don't bother to learn correct usage.

There is a direct comparison with its Spanish counterpart - you do not respond to "¿Qué tal estás?" with "Estoy bueno", and nor should you in English.

I suppose in theory the appropriate response to "I'm good" should be "I'll be the judge of that!", but I've always resisted the temptation (so far!).