Portuguese has 9 oral vowel sounds and 19 consonants. In some places one or more of these sounds has merged with another, to render fewer. (For example, Brazilian Portuguese only employs 8 oral vowel sounds). Additionally, linguists have identified five nasal vowels, which correspond to five of the oral vowels. There are additionally ten oral diphthongs and five nasal diphthongs.
The consonants have remained fairly stable since medieval times ("Old Portuguese"). The affricates /ts/, /dz/, /t?/ and /d?/ have yielded to their fricative cousins, that is, /s/, /z/, /?/ and /?/. But they have not merged further with each other. The following table displays the consonants of Portuguese in IPA format.
A number of important dialectic changes have occurred between Portugal and Brazil. In Brazil the /t/ and the /d/ become [t?] and [d?] before /i/ and /ĩ/. (This is the "tch" and "dg" sound instead of a pure dental "t" or "d" as in Portugal.) The /l/ in final position in Brazil tends not to be fully pronounced, and becomes a [u?] (turning "leal" for example into something that sounds more like "leao"). The "nh" sound, as in "ninho" (meaning child, and spelled in Spanish as "niño") often looses the "n" and becomes more like "KNEE-yo". In IPA symbols, the /'niɲu/ is pronounced ['nĩj~u]. The Rio (Carioca) accent and those surrounding it (Fluminense for the accent around Guanabara, as the State of Rio used to be called) has a tendency to "sh" the "s" sound, somewhat like the tendency in Castilian Spanish. A similar phenomenon can be observed in parts of Portugal. In São Paulo and points further south, the /s/ and /z/ phonemes are cleaner and purer. This "sh" tendency comes from forming the sibilants in the post-alveolar regions of the mouth rather than on the alveolar ridge itself. The /s/ becomes an /?/ before voiceless consonants. It would normally be a /z/ before voiced consonants, and becomes a /?/ instead. Finally, the rhotic phoneme - the "guttural R" in Portuguese - is similar to the Gallic "R." It is a uvular fricative, rolled out of the back of the throat (not trilled or tripped like the Spanish "r"). How hard or soft the "r" is spoken varies widely among accents, from a bland velar "huh" at one extreme, to almost a glottal growl at the other. The Rio accent in Brazil is most noted for a very strong "r," especially when it comes in accented position after a back vowel (like open "o"). The word "importa" for example ("to matter") can be pronounced with such emphasis on the "R" that it sounds like the speaker is clearing his throat between the "po" and the "ta." Another example is the word, "amor" (love), which, with a Rio accent, can have a scraping "R" that overpowers all the letters that come before it.
The vowels and diphthongs of Portuguese are more complicated than the consonants. The following diagram shows the position of the nine recognized oral vowels and their five nasal colleagues. The "ω" sound is a central vowel - a kind of neutral "eh" sound with more "a" than a schwa. It is very common in Portugal, and hardly ever heard in Brazil. The distinction between open and closed "e" and open and closed "o" is indicated diacritically as (é; ê) and (ó;ô) respectively, and phonetically as (ε,e) and (? ,o).
Diphthongs occur frequently, but are usually spelled the way they are pronounced (that is, the "ay" sound as in "hay" in English is consistently spelled "ei" in Portuguese. The nasal diphthongs occur in combination with certain consonants (like "m" and "n"). They occur at the end of a syllable (as in "pensar" (to think) which for English speakers is pronounced something like "peng-SAR). They are particularly evident at the end of a word, as in "também" (also) which is pronounced something like "tom-BENG" by an English speaker).