Overview
The spelling of Portuguese is largely phonemic, but some phonemes can be spelled in more than one way. In ambiguous cases, the correct spelling is determined through a combination of etymology with morphology and common tradition, so there is not a perfect one-to-one correspondence between sounds and letters or digraphs. Knowing the main inflectional paradigms of Portuguese, and being acquainted with the orthography of other languages of Western Europe, can be helpful in this regard.
In the remainder of this article, the phrase "at the end of a syllable" can be understood as "before a consonant, or at the end of a word".
Read more about this topic: Portuguese Orthography