text: # Subsets of sets containing empty set [duplicate]
  
  Why is $\{\emptyset\}$ not a subset of $\{\{\emptyset\}\}$?
  
  It contains this element, but why is it not a subset?
  
  -
  
  ## marked as duplicate by Rory Daulton, Claude Leibovici, Eric Wofsey, Joel Reyes Noche, Jack's wasted lifeFeb 5 at 12:19
  
  You're trying to interpret the word "contain" too broadly. For example, a library may be said to contain letters, words, sentences, paragraphs, and chapters; but when we think of a library as a set, we generally think of it as a set of books, so only the books are members of the set, and not the piecemeal contents/components of the books. – Scott Feb 4 at 18:25
  In addition to the excellent answers below, look at math.stackexchange.com/questions/1281436/… -- especially part 3 of the question. – David K Feb 4 at 22:41
  $\in\ne\subset$. – Martín-Blas Pérez Pinilla Feb 5 at 7:26
  Incidentally, there is a word for a set of which every element is also a subset, and that word is "transitive". $\{\{\emptyset\}\}$ is not a transitive set, but $\{\{\emptyset\},\emptyset\}$ is. – Steve Jessop Feb 5 at 11:05
  
  It is not a subset because its element $\emptyset$ does not belong to the set $\{\{\emptyset\}\}$.
  
  -
  
  The element $\{\emptyset\}$ and the element $\emptyset$ are different.
  
  $\{\emptyset\}$ is an element of $\{\{\emptyset\}\}$, whereas $\emptyset$ is not.
  
  A subset is a set whose every element is also a part of the given set.
  
  Thus, the subsets of $\{\{\emptyset\}\}$ are $\{\{\emptyset\}\}$ and the empty set $\{\}$, also denoted by $\emptyset$.
  
  EDIT:
  
  In one sentence, (Thanks to @Henry)
  
  $\{\{∅\}\}$ has a single element $\{∅\}$ and two subsets $\{\{∅\}\}$ and $∅$, while $\{∅\}$ has a single element $∅$ and two subsets $\{∅\}$ and $∅$.
  
  -
  You could say that $\{\{\emptyset\}\}$ has a single element $\{\emptyset\}$ and two subsets $\{\{\emptyset\}\}$ and $\emptyset$. Meanwhile $\{\emptyset\}$ has a single element $\emptyset$ and two subsets $\{\emptyset\}$ and $\emptyset$. – Henry Feb 4 at 22:49
  @Henry That's a nice way of saying it, have added it to the answer. Thank you. – GoodDeeds Feb 5 at 10:43
  
  You can think of sets like plastic bags if you want; the empty set is just a plastic bag with nothing in it, $\{\emptyset\}$ is a plastic bag with another plastic bag in it, and $\{\{\emptyset\}\}$ is three layers of plastic bags.
  
  The element relation $A\in B$ means that you could open up bag $B$ and take out $A$.
  
  The subset relation $A\subset B$ means that every object that you could directly take out of $A$ can also be directly taken out of $B$.
  
  So, look at $\{\emptyset\}$. You can "open it up and" take out $\emptyset$, but you can't do that with $\{\{\emptyset\}\}$. Therefore, $\{\emptyset\}\not\subset \{\{\emptyset\}\}$.
  
  -
  You didn't define B, which makes this answer a bit hard to follow. – djechlin Feb 4 at 22:08
  @djechlin Fixed, thanks! – Deusovi Feb 4 at 22:24
  sure you can, just open the bag and take the plastic bag with nothing inside out. – djechlin Feb 4 at 22:42
  @153330 Then you have fun with whatever visualization or lack of visualization you want. – Deusovi Feb 5 at 3:02
  The bag layers' count would be more obvious if you replace $\emptyset$ with$\{\,\}$ after the first use. – CiaPan Feb 5 at 10:16
metadata: {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}