The letter "i"

As you may or may not know: In Portuguese, the general rule of the stressed syllable in a word is penultimate*, unless otherwise marked.

(Unmarked: alguma {(AW-GOO'-MAH) or [aw.'gu.ma]}, preciso {(PDEH-SEE'-ZU) or [pɾe.'si.zu]}; Marked: avô {(AH-VOHW') or [a.'vo]}, avó {(AH-VAW') or [a.'vɔ]})

There is another exception:
When a Portuguese word ends in the letter "i", the final syllable is automatically stressed.

For example:
Tupi is pronounced TOO-PEE' or [tu.'pi] (for you linguistics buffs!)
guri is pronounced GOO-REE' or [gu.'ɾi]
 
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*penultimate:
Function: adjective
1: next to the last penultimate
chapter of a book>Thanks to M-W.com and Don Blaheta (for the IPA flap r)