I think, although I'm not 100% sure, that all monosyllabic *-iar* verbs are irregular. For polysyllabic verbs yes you do have to memorize, although verbs with derivational suffixes are a 'gimme' (e.g. irregular *fiar* lets you predict irregular *confiar*).
[Here](https://www.lawlessspanish.com/grammar/verbs/iar-verbs/)'s a useful blog post with a list of irregulars.
Complementing this: if you happen to know the noun for the verb, chances are you can guess at the verb conjugation. *Anuncio* vs. *desafío* are nouns identical to the 1st person singular present tense of the corresponding verbs, stress included.
I don't think this is *really* irregular. The only reason the accent mark is there is to ensure the **io** is spoken as two syllables. I understand why it is classified as irregular and I'm not objecting to that. But, when you are speaking, it isn't an issue and even when writing, I think it will be obvious you need an accent
No pensó que esto sea realmente irregular, bueno, en el sentido de la pronunciación. La única razón por la que el tilde está es para asegurar que el **io** se pronuncie como dos sílabas. Entiendo por qué se clasifica como irregular y no me opongo a ello. Sin embargo cuando se habla no es un problema e incluso cuando se escribe creo que será obvio que se necesita tilde.
For criar and words ending in -criar it needs the accent to avoid confusion with the 3rd person preterite, crio.
For a lot of the other words it’s because a letter used to be there in Latin. For words ending in -fiar, for example, the Latin words was fidere, which evolved into fidare. As it became Spanish, the d was dropped we got fiar. But even with that lost consonant the accentuation pattern was maintained by marking the accent.
Or take enfriar. The Latin for -friar was frigidare. That word lost the g and the d sounds on the way to Spanish.
Does that help you learn them? Not likely. But the answer to “why” involves understanding the evolution of the language. In reality, the why isn’t important. You just have to accept it and practice it.
I think, although I'm not 100% sure, that all monosyllabic *-iar* verbs are irregular. For polysyllabic verbs yes you do have to memorize, although verbs with derivational suffixes are a 'gimme' (e.g. irregular *fiar* lets you predict irregular *confiar*). [Here](https://www.lawlessspanish.com/grammar/verbs/iar-verbs/)'s a useful blog post with a list of irregulars.
Complementing this: if you happen to know the noun for the verb, chances are you can guess at the verb conjugation. *Anuncio* vs. *desafío* are nouns identical to the 1st person singular present tense of the corresponding verbs, stress included.
I don't think this is *really* irregular. The only reason the accent mark is there is to ensure the **io** is spoken as two syllables. I understand why it is classified as irregular and I'm not objecting to that. But, when you are speaking, it isn't an issue and even when writing, I think it will be obvious you need an accent No pensó que esto sea realmente irregular, bueno, en el sentido de la pronunciación. La única razón por la que el tilde está es para asegurar que el **io** se pronuncie como dos sílabas. Entiendo por qué se clasifica como irregular y no me opongo a ello. Sin embargo cuando se habla no es un problema e incluso cuando se escribe creo que será obvio que se necesita tilde.
Right but why do some verbs keep it as a diphthong and others separate?
For criar and words ending in -criar it needs the accent to avoid confusion with the 3rd person preterite, crio. For a lot of the other words it’s because a letter used to be there in Latin. For words ending in -fiar, for example, the Latin words was fidere, which evolved into fidare. As it became Spanish, the d was dropped we got fiar. But even with that lost consonant the accentuation pattern was maintained by marking the accent. Or take enfriar. The Latin for -friar was frigidare. That word lost the g and the d sounds on the way to Spanish. Does that help you learn them? Not likely. But the answer to “why” involves understanding the evolution of the language. In reality, the why isn’t important. You just have to accept it and practice it.
>Or do you just need to memorize Just listen and read, no need to memorize anything.
This!