minor difference
Often used in the phrase 大同小異 (largely the same with only minor differences). As a standalone noun, it is somewhat formal and less common in casual speech.
There are minor differences between their opinions, but they are basically the same.
この二つの製品は小異を除けばほとんど同じだ。
These two products are almost the same except for minor differences.
essentially the same; much of a muchness
Compound of 小 (small) and 異 (difference). The word is used in classical Chinese-derived expressions and is most familiar from the four-character idiom 大同小異.