The Portuguese orthography is based on the Latin alphabet, and makes use of the acute accent, the circumflex accent, the grave accent, the tilde, and the cedilla, to denote stress, vowel height, nasalization, and other sound changes. Accented letters and digraphs are not counted as separate characters for collation purposes.
A full list of sounds, diphthongs, and their main spellings, is given at Portuguese phonology. For the main values of each letter and digraph, see Portuguese alphabet. This article addresses the less trivial details of the spelling of Portuguese, as well as other issues of orthography, such as accentuation.
Read more about Portuguese Orthography: Overview, Sounds With More Than One Spelling