Colon in Emacs Lisp

Question

I came across this example:

(setq h-data '((:num 1 :key "apple")
               (:num 9 :key "berry")
               (:num 2 :key "cactus")
               (:num 5 :key "dog")
               (:num 4 :key "frog")))

The source said that this is a property list. So, I looked up the manual and did not notice any syntax using a colon. What is this syntax? Is :num different from 'num? Where is this syntax described in the manual?

You probably mean "colon", not "column". See [Symbol Type](https://www.gnu.org/software/emacs/manual/html_node/elisp/Symbol-Type.html). — choroba, Aug 18 '17 at 09:53
@choroba: please post your comment as an answer (with a little bit more that explains what a keyword is). — Dan, Aug 18 '17 at 10:06
@Dan With the change, my question is a duplicate of this (just found now): https://emacs.stackexchange.com/q/12142/16048 — AlwaysLearning, Aug 18 '17 at 10:08

score 3 · Accepted Answer · answered Aug 18 '17 at 10:07

See Symbol Type:

A symbol whose name starts with a colon (:) is called a keyword symbol. These symbols automatically act as constants, and are normally used only by comparing an unknown symbol with a few specific alternatives. See Constant Variables.

Colon in Emacs Lisp

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