After all these years, I’m still refining my knowledge of Spanish. Just this week I learned a subtle detail about an obscure but genuine rule of Spanish: the occasional change of y and o (‘and’ and ‘or’) to e and u. Y and o are pronounced ee and oh, and this change happens when one of these words comes before a word that begins with the same sound. So, for example, we say bonita e inteligente ‘pretty and smart’ and siete u ocho ‘seven or eight’ to keep the vowels from merging into each other at the boundary of y and inteligente, and likewise of o and ocho.
We have a similar phenomenon in English, where a changes to an before words that begin with a vowel, so that we say, for example, an apple and an elephant as opposed to a pear and a zebra. Just as in the Spanish case, this prevents the vowel of the word a from running into the first vowel of the following word. The linguistic term for such a change is dissimilation.
I would describe the y/o rule as “basic advanced Spanish”, meaning that anyone who wants a good command of the language will eventually learn it. I always get a kick out of teaching it: students are surprised to learn that these basic words, which they may have been using for years, have two different forms. That’s when I bring in the a pear/an apple example from English and really blow their minds.
The detail that I just learned has to do with words that begin with hie-, such as hierro ‘iron’. The letter h is silent in Spanish, so that y changes into e before other words that begin with hi-, as in aguja e hilo ‘needle and thread’. However, in words like hierro the i takes on a consonantal y sound — that is, the word is pronounced yero — so there is no need for the y > e change. A good example is the phrase madera y hierro ‘wood and iron’.
Here’s the rule as explained in the Real Academia Española’s Ortografía:
“La y copulativa mantiene su forma cuando la palabra que sigue a la conjunción comienza por un diptongo de /i/ + vocal, ya que en esos casos la /i/ del diptongo no es plenamente vocálica, sino que se acerca, en la pronunciación espontánea, al fonema consonántico /y/. Al no confluir ya dos fonemas vocálicos iguales, la y copulativa no necesita transformarse en e: madera y hierro [madéra i yérro], agua y hielo [água i yélo], alfa y iota [álfa i yóta].”
By the way, no Spanish words begin with ie-, just as none begin with ue-. At the beginning of a word the ie sequence is always spelled hie- or ye- (as in yeso ‘plaster’), and the ue sequence, hue- as in huevo ‘egg’. A fun fact for your Tuesday!
Many thanks to reader and friend Daniel Nappo for bringing this topic to my attention.