Vowels to be stressed are presented in red in this article.
Only one stress in a word (Exception: Words ending with ‘-mente’)
If there is a written accent, stress on that vowel (and ‘-mente’) and forget about all the rules:
General rule of stress on words with no written accent
Stress on the second to the last syllable if the word ends in a vowel or ‘n’, or ‘s’
Stress on the last syllable if the word ends in a consonant other than ‘n’ or ‘s’
Strong and weak vowels
Strong Vowels: a, e, o
Weak Vowels: i, u
One syllable is comprised of one vowel or diphthongs (two adjacent vowels: one strong vowel and one weak vowel or two weak vowels):
Diphthongs – one syllable
1. Diphthongs (one strong and one weak adjacent vowels):
ai, ei, oi, au, eu, ia, ie, io, ua, ue, uo
Stress on the strong vowel:
2. Diphthongs (two weak adjacent vowels):
Stress on the second weak vowel:
Two adjacent strong vowels are two syllables
ideal – i-de-a-l
The default stress is on a because the word ends in ‘l’ which is not ‘n’ or ‘s’ or a vowel. So stress should be on the last syllable.
idea – i-de-a
The default stress is on e because the word ends in ‘a’ which is a vowel. So stress should be on the second to the last syllable.
leer = le-er
feo – fe-o
Only one stress in a word (Exception: Words ending with -mente)
Let’s review the rules:
No written accent on the plural of these words (in order to maintain the stress on the same vowel both on singular and plural)
Words ending with ‘-ión’ with written accent:
Plurals of these words do not need a written accent because of one extra syllable (‘es’) at the end. As these words end in ‘s’, the default stress will be on the second to the last syllable which is ‘io’. As ‘io’ is a combination of a weak vowel and a strong vowel, the default stress will be on the strong vowel which is ‘o':
A few more words with stress on same vowel both on singular and plural:
botón – botones
inglés – ingleses
salón – salones
melón – melones
A different case: Written accent is used only when it is plural (in order to maintain the stress on the same vowel both on singular and plural)
orden – órdenes
Stress is on ‘o’ in both the cases. As the word ‘orden’ ends in ‘n’, the default stress will be on the second to the last syllable which is ‘o’ and the word ‘órdenes’ has a written accent on ‘ó’, so the stress should be on ‘o’.
el examen – los exámenes
el crimen – los crímenes
Let’s analyze one more word:
también – here we have ‘a’ and ‘ie’. The written accent on ‘é’ is telling us not to stress on the default vowel ‘a’ but to stress on ‘ie’ (‘e’ being the strong vowel, written accent is placed on ‘ié’). It is not asking us to separate ‘i’ and ‘e’.
to be continued…