These three belong to three different clubs.

First one, very popular, is the singles-only club. It is closed for new membership.

Second one, very useful, is for singles and couples. It is open for new members but it is very hard to get in now.

Unlike the first two clubs, the third club is different for these three. The three singles are related to each other. Especially, two of them are talked about constantly and daily.

Outside these clubs, when the three come together, you are looking at very popular food!

Who are they? What are the three clubs?


They are not words

  • 1
    $\begingroup$ Since they are single, should they consider dating each other? But wait... someone's gonna be the third wheel... $\endgroup$ Commented Aug 21, 2019 at 14:28
  • $\begingroup$ @OmegaKrypton Until recently, the 2nd club used to provisionally allow trios, but then they made them drop their third wheels. $\endgroup$ Commented Aug 21, 2019 at 20:47
  • $\begingroup$ In the third club, I think only one of them is constantly talked about daily, unless you're a scientist. (The third one only if there happen to be some Americans around.) $\endgroup$ Commented Aug 24, 2019 at 6:37

1 Answer 1


The three singles are

The letters c, f and k

The first club is

The (latin) alphabet, which seems to have settled at 26 letters, and can be considered closed.

The second club is

The periodic table, which consists of singles (H, C, O, etc) and pairs (Na, Mg etc). C is the symbol for carbon, F for Fluorine, K for Potassium. Each successive element contains one more proton in the nucleus, so it is currently only possible to join by having more than 118 protons, but these elements are increasingly unstable.

The third club is

Physical symbols for Temperature. C/F/K stand for Celsius, Fahrenheit and Kelvin, but only C and F are used daily for discussing the weather

Putting them together gives the popular food


  • 1
    $\begingroup$ Great job @Fillet. I think you should also comment on why the first is closed and the second may be open but very hard to get in $\endgroup$
    – DrD
    Commented Aug 21, 2019 at 14:08

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