While researching the origin of the three conjugation classes of Spanish — ar, er, and ir — I recently turned to the lovely folks at the wordreference.com Spanish-English vocabulary forum to help me think of pairs of Spanish verbs that differ only in their conjugation class. The only two I had thought of were sentar/sentir and crear/creer.

These pairs are a nice reminder that the conjugation classes, by themselves, are void of meaning. Please see my original post (link above) for an example of a language (Hebrew) where the same verb root can appear in more than one conjugation class, with each class adding a predictable nuance to the verb root’s core meaning.

Here is my full list, which I will continue to edit as I learn of more. Note that there are no triplets on the list, and that all the pairs contrast -ar with either -er or -ir. This may be a coincidence, but the fact that -er and -ir verbs have almost identical conjugations (the only difference is in the nosotros and vosotros present indicative) would make triplets or an -er/-ir contrast hard to learn and to maintain.

Please let me know if can think of any more.

• asentar/asentir
• crear/creer
• fundar/fundir
• mentar/mentir
• molar/moler
• morar/morir
• parar/parir
• podar/poder
• rendar/rendir (render is also in the RAE, but only as an antiquated form of rendir).
• salar/salir
• sentar/sentir
• solar/soler
• sumar/sumir
• tejar/tejer
• vivar/vivir