You will hopefully find that your favourite Spanish guide or dictionary has a section on pronunciation. If that section is in any way typical, it will deal largely with the pronunciations of individual sounds of the language. It’s surely a helpful starting point to consider how to pronounce, say, “the Spanish rolled r” or “the Spanish ‘i’ vowel” in isolation, or in certain example words. But your strategy for improving your pronunciation also needs to go beyond this letter-by-letter or sound-by-sound approach.
If you want your speech to sound as natural and intelligible as possible, the rhythm of your speech can be just as important as, say, the quality of individual vowels. As an illustration of the importance of rhythm in speech, think in English about how you’d differentiate a ‘lighthouse keeper’ from a ‘light housekeeper’. In this article, I’ll outline two important elements of rhythm and how they work in Spanish: syllabification and stress. Syllabification is the process of organising the sounds of a word or utterance into syllables, and can differ a little from language to language. Informally, when we clap a word or phrase, we clap once to each syllable.
By ‘stress’ we mean making certain syllables prominent relative to others around them. For example, in English, the first syllable is stressed in the words ‘Inca’ and ‘impotent’, whereas the second syllable is stressed in ‘incur’ and ‘important’.
A key to giving your Spanish a more natural rhythm is to understand a process called diphthongisation: that is, making two vowels share a single syllable. Whenever you see a ‘i’ or ‘u’ vowel next to another vowel in Spanish, you need to think about diphthongisation:
(1) if the ‘i’ or ‘u’ is the stressed vowel– usually written with an accent, as in ‘María’, ‘país’ (“country”), ‘dúo’ (“duet”) or ‘búho’ (“owl”)– then the two vowels will form separate syllables: Ma.rí.a, pa.ís, dú.o, bú.(h)o (remember, the Spanish letter ‘h’ isn’t pronounced);
(2) otherwise, the ‘i’ or ‘u’ will usually be pronounced in the same syllable as the vowel next to it: so Spanish speakers would pronounce ‘San Die.go’ as three syllables, not four as in English ‘San Di.e.go’; Spanish ‘u.sual’ is two syllables, compared to English ‘u.su.al’. In these cases the ‘i’ or ‘u’ “glides” into the other vowel, a bit like an English ‘y’ or ‘w’. In other cases, it could “glide out” of the other vowel, as in ‘au.la’ (“classroom”, “lecture hall”), ‘seis’ (“six”).
Especially in some parts of Spain, there is some variation to (2): there’s a greater tendency towards separate syllables at the beginnings of words (e.g. ‘bi.ó.lo.go’, though ‘bió.lo.go’ is also possible), and where one word with definitely separate syllables has an influence on another by analogy. Thus, the word ‘ví.a’ (“road”, “route”, “way”), always pronounced as two syllables, tends to influence speakers’ pronunciation of ‘vi.a.ble’ (“viable”); ‘rí.e’ (“he/she laughs”) tends to influence ‘ri.en.do’ (“laughing”), whereas on the other hand speakers would generally pronounce ‘sien.do’ (“being”) as two syllables.
The ‘vosotros’ verb forms and triphthongs
Note that the endings of ‘vosotros’ verb forms always contain a diphthong. In a few cases, an ‘i’ or ‘u’ vowel can occur both before and after another vowel, resulting in a triphthong: three vowels sharing a syllable. Examples include ‘vosotros’ form of regular -iar verbs (so ‘(vosotros) cambiáis’ will be pronounced in just two syllables: ‘cam.biáis’) and a few other words such as ‘buey’ (“ox”; “idiot”) and ‘Pa.ra.guay’.
Syllabification in normal speech
The patterns we’ve presented above apply to what we might call ‘careful’ speech: for example, the style used by a newsreader reading from the autocue. In normal, relaxed speech, diphthongisation goes a couple of stages further:
(1) any two vowels next to each other tend to share a syllable;
(2) even across word boundaries, two vowels can share a syllable.
So in careful speech, ‘poeta inglés’ (“English poet”) would be syllabified ‘po.e.ta.ing.lés’, in five syllables, but in normal, relaxed speech would tend to be ‘poe.taing.lés’; ‘come y toma’ (“eat and drink”) would be ‘co.mei.to.ma’; ‘mi amigo’ would be ‘mia.mi.go’ etc. The word ‘zanahoria’ (“carrot”) is often pronounced as three syllables, ‘za.na(h)o.ria’: as mentioned before, the ‘h’ isn’t pronounced and doesn’t affect syllabification.
In general, every Spanish word has exactly one stressed syllable (with a couple of exceptions we’ll consider in a moment). The “default” is for the next-to-last syllable to be stressed, and is reckoned to be the case for about 80% of words; words ending in a consonant except plural -s are regularly stressed on the final syllable. Where the stressed syllable of a word isn’t predicted by these rules– and even in some cases where it is– the stressed syllable is marked with a written accent, as in ‘fácil’ (“easy”), ‘métrico’ (“metric”). But even when the regular rules apply, subtly, we must apply the above diphthongisation rules in counting syllables. Thus, in ‘monopolio’ (“monopoly”), it is the next-to-last ‘o’ that is stressed: mo.no.pó.lio, since the final -lio forms a single syllable. In the word ‘continuo’, the ‘i’ is stressed, as the word is syllabified ‘con.ti.nuo’, in three syllables, not four (unlike English ‘con.ti.nu.ous’).
A couple of exceptions to the one-stress-per-word rule are worth mentioning. Firstly, a few “function words” don’t generally have any stressed syllable at all. These include:
– possessives (‘mi’, ‘tu’ etc);
– clitic pronouns (the pronouns that come before the verb: ‘me’, ‘te’, ‘se’ etc);
– single-syllable prepositions (‘de’, ‘por’, ‘a’ etc);
– various conjunctions when not used in a direct question (‘cuando’, ‘mientras’, ‘quien’ etc).
Where these non-stress-carrying words end in a vowel, they’re ripe candidates for forming a diphthong with the following word in rapid speech, as in ‘mi amigo’ (“my friend”: mia.mi.go), ‘me apuro’ (“I’ll hurry up”: mea.pu.ro) ‘de otra manera’ (“another way”: deo.tra.ma.ne.ra).
Finally, Spanish adverbs ending in -mente are the greediest of words, and generally have two stressed syllables. In effect, the suffix -mente is treated as a word in its own right in terms of stress (and actually derives from the word for ‘mind’); then, the adverb carries another stress in the place of the corresponding adjective. For example, ‘fácil’ (“easy”) is stressed on the first syllable; ‘fácilmente’ (“easily”) is stressed on both the first and next-to-last syllables. The word ‘frecuente’ (“frequent”, “common”) is regularly stressed on the next-to-last syllable (the ‘cuen’, containing diphthong of course!); the adverb ‘frecuentemente’ (“frequently”, “commonly”, “often”) on both the ‘cuen’ and ‘men’.
In this article, we’ve presented some pointers towards improving the rhythm of your Spanish pronunciation. If you can get into the habit of following the patterns we’ve presented, this will help make your Spanish sound more natural and intelligible to native speakers.
 This is obviously an informal, intuition-based definition of ‘syllable’. The Spanish pronunciation section of the Español-Inglés web site gives a more formal definition.
 For more details and examples, see: Chitaron, I. & Hualde, J. I. (2007), “From hiatus to diphthong: the evolution of vowel sequences in Romance” in Phonology (24):37-35.
 Source: Alcoba, S. & Murillo, J. (1998), “Intonation in Spanish” in “Intonation Systems: A Survey of Twenty Languages”, CUP.