Words that have an accent on the antepenultimate syllable
Palabras esdrújulas are those that have the stress on the antepenultimate syllable (i.e third syllable from last), for example:
In pronunciation, we often talk about "acento" and "tilde". We refer to the "acento" to say which syllable receives the highest intensity when pronouncing the word. However we talk about "tilde" when we refer to the "written or typed accent" on the highest intensity syllable of the word.
camiseta, mesa, árbol, túnel, beso
All these words are accentuated on their penultimate syllable, but only árbol and túnel have a "tilde" [´]