A subset is a smaller group that sits completely inside a bigger group. Every member of the subset is also a member of the big group — that is the whole point. Cats are a subset of animals; every cat is an animal. The word comes out of mathematics, where it is exact: set A is a subset of set B if every single thing in A is also in B.

A subset is a smaller group subset 是一個比較小的群體 that sits completely inside a bigger group完全包含在一個更大的群體裡面 Every member of the subset is also a member of the big group subset 裡的每一個成員也都是那個大群體的成員 — that is the whole point這就是重點所在 Cats are a subset of animals貓是動物的一個 subset every cat is an animal每一隻貓都是動物 The word comes out of mathematics這個字源自數學 where it is exact在數學裡它的定義很精確： set A is a subset of set B集合 A 是集合 B 的 subset if every single thing in A is also in B只要 A 裡的每一個元素也都在 B 裡

Outside maths it keeps that shape but gets used more loosely, especially in business, science and computing: 'a small subset of our customers', 'a subset of the data', 'only a subset of the features work on the old phone'. In that everyday use it often carries a quiet extra meaning of 'not all of them, only some' — when a company says 'a subset of users were affected', part of what they are doing is telling you the number is small.

Outside maths在數學之外 it keeps that shape but gets used more loosely它保留這個概念，但用得比較鬆散 especially in business, science and computing尤其在商業、科學、電腦領域： 'a small subset of our customers', 'a subset of the data', 'only a subset of the features work on the old phone'像是「a small subset of our customers」、「a subset of the data」、「only a subset of the features work on the old phone」 In that everyday use在這種日常用法裡 it often carries a quiet extra meaning of 'not all of them, only some'它常常悄悄多帶一層「不是全部，只有一部分」的意思 — when a company says 'a subset of users were affected'當公司說「a subset of users were affected」 part of what they are doing is telling you the number is small他們有一部分用意就是在告訴你這個數字很小

It is a written, thinking-out-loud sort of word. In normal talk people say 'some of', 'part of', 'a certain group of'.

It is a written, thinking-out-loud sort of word這是偏書面、邊想邊說那種調調的字 In normal talk people say 'some of', 'part of', 'a certain group of'一般說話大家會說「some of」「part of」「a certain group of」

Notice that a subset is not the same as a piece broken off. A slice of cake is a part of the cake but we would not call it a subset; subsets are about members of a group, things you could count and list.

Notice that a subset is not the same as a piece broken off要注意 subset 跟「被切下來的一塊」不是同一回事 A slice of cake is a part of the cake一片蛋糕是蛋糕的一部分 but we would not call it a subset但我們不會叫它 subset subsets are about members of a group subset 講的是一個群體裡的成員 things you could count and list是你可以一個一個數、一個一個列出來的東西

Also, strictly, a group counts as a subset of itself — maths allows that — though in real use people almost always mean a smaller-than-the-whole group.

Also, strictly另外，嚴格來說 a group counts as a subset of itself一個群體本身也算是自己的 subset — maths allows that數學上是允許的 though in real use people almost always mean a smaller-than-the-whole group不過實際使用時，大家幾乎都是指比整體小的那種群體