One Small Thing
One Thing, One Small Object, One Object
noun
The counter 個, which means individual on its own, refers to "an individual thing." This is usually a small thing, so it's used to count small things. This word here talks about one individual. A better way to translate that would be to call it one small thing.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. The いち gets shortened, but I bet you knew that already.
しょうがないなぁ。一個だけだよ？
Alright, alright. Just one, okay?
え、このイチゴ、一個千五百円だって！
What? These strawberries are 1,500 yen each!
シュークリーム、ちゃんと一人一個ずつあるから、取り合わなくていいよ。
There's one cream puff for each person, so there's no need to fight over them.