Naïve
The word is sometimes spelt in English without the French double dot on the letter i, "naive", due to the default settings for typing in English lacking it.   It is an adjective.  The noun is naïveté, but is sometimes spelt naïvety in English.  It is similar in meaning to the word "innocent" and is not always a negative quality in that being naïve implies a lack of acquired prejudice.