When you look up the Italian word "di" in Google Translate, you get the following screen:
To the right, there are some English translations of the word, and each English translation has again some Italian translations, which can be regarded as (more or less) synonyms of "di".
On the left side, there are some other words which are labelled as synonyms. However, the word "di" on the left side is understood in a way that's a bit more special than that on the right side: It's the word "di" in "buon di" (meaning "day"), and the second person imperative of "dire" (e.g. "dimmi!"). So we get "giornata" and "significare" as synonyms.
Is there a specific reason why Google Translate shows these synonyms in this way? When I think of synonyms of "di", the words on the right side would come to my mind before those on the left side. But those on the left side are marked as "synonyms", and those on the right side not.