how do you know if a verb is radically changing?

Question

not really sure how you're supposed to tell if a verb is radically changing or not, for example tener and saber

Answer 1

how you're supposed to tell if a verb is radically changing?

If it's having hot flashes, complains about the most trivial problems in life, and later runs away to Florida for a Spa Getaway.

Okay, only kidding...welcome to the forum.

Radical verbs, a.k.a., stem-changing have a change in the vowel when it is stressed in the present tense. These verbs do not so change in any other tense —except for -ir verbs, which experience a stem change in the -ndo form, in the present subjunctive and in the preterit.

o > ue (acuesto)

e > ie (empiezo)

e > i (pido)

u > ue (juego)

I was going to say that you have to ask it if its a radical or not. But your answer is better. - gringojrf, Apr 9, 2012

Answer 2

As far as I know, the only way to remember such verbs is to try to master their conjugation table one at a time, i.e., there's no shortcut. After a certain time though, you will notice that although they are irregular verbs, there is some kind of rule in that irregularity. For example, tener - 1st person preterite - tuvE , 3rd person preterite tuvO poner- 1st person preterite - pusE , 3rd person pretetive pusO

Probably a native/advanced speaker can give some more insights on this.