There are a few key historical reasons for the differences between Portuguese spelling and pronunciation:
- Portuguese orthography was standardized in the 16th century, while the language continued evolving phonologically over centuries. This led to spelling-sound inconsistencies.
- Portuguese was influenced in its early formation by Galician-Portuguese and Leonese Spanish dialects from the Iberian Peninsula. These had phonological traits like Latin-derived postalveolar consonants that Modern Portuguese lost.
- When the Portuguese language was developing, syllable and stress patterns played a bigger role in pronunciation versus just letters. Over time, stress shifts occurred.
- The incorporation of vocabulary from other languages like French, Italian, Arabic, etc. introduced new sounds without changing spellings.
- Portugal’s political union with Spain from 1580-1640 saw Portuguese writing influenced by Spanish convention, solidifying spellings while sounds drifted.
- Portuguese colonies worldwide led to development of distinct pronunciation norms without spelling updates in Portugal.
- There was resistance to spelling reforms that proposed bringing orthography more in line with modern phonology. Tradition won out.
So while spelling was fixed earlier, pronunciation naturally evolved, leading to discrepancies remaining today between what’s written and spoken in Portuguese. The language’s complex historical influences play a role.