This is the 3864th most frequent Japanese word.
ウニ
Sea urchin.
『ウニ』 in this sentence refers to the biological sea creature, showcasing its usage as a noun referring to the animal.
ウニは海に住んでいる生き物です。
Sea urchins are creatures that live in the ocean.
Here, 『ウニ』 is used to refer to the sea creature as a culinary ingredient, emphasizing a gastronomic context.
寿司屋で新鮮なウニを食べました。
I ate fresh sea urchin at the sushi restaurant.
In this instance, 『ウニ』 is used metaphorically to describe someone's personality, making a comparison to the spiny and reserved nature of sea urchins.