95% of italian words with accent use the left-facing accent (╰ ) (grave)
"Perché" (why/because), ventitré (twenty-three) use the right-facing accent (╯) (acuto), but IMHO few people in italy know the real difference in pronounciation
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Are you referring to "o" and "oppure" ? If you are, there is one more "ovvero" :)
There is no grammatical difference between "o" and "oppure".
However if you use oppure than you are stressing the idea of choice, while by using "o" you're a bit more indifferent whether you'll choose tea or coffee.
On other hand "ovvero" would translate to "or rather"