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    <p>The good manual is <a href="http://gigamonkeys.com/book/programming-in-the-large-packages-and-symbols.html" rel="nofollow">Chapter 21 of PCL</a>.</p> <p>Answering your questions briefly:</p> <ul> <li><p>keywords are exported <strong>symbols</strong> in <code>keyword</code> package, so you can refer to them not only as <code>:a</code>, but also as <code>keyword:a</code></p></li> <li><p>keywords in function argument lists (called <code>lambda-list</code>s) are, probably, implemented in the following way. In presence of <code>&amp;key</code> modifier the <code>lambda</code> form is expanded into something similar to this:</p> <pre><code>(let ((key-param (getf args :key-param))) body) </code></pre></li> <li><p>when you use a keyword to name a package it is actually used as a <code>string-designator</code>. This is a Lisp concept that allows to pass to a certain function dealing with strings, that are going to be used as symbols later (for different names: of packages, classes, functions, etc.) not only strings, but also keywords and symbols. So, the basic way to define/use package is actually this:</p> <pre><code>(defpackage "KEY-PARAM" ...) </code></pre> <p>But you can as well use:</p> <pre><code>(defpackage :key-param ...) </code></pre> <p>and</p> <pre><code>(defpackage #:key-param ...) </code></pre> <p>(here <code>#:</code> is a reader macro to create uninterned symbols; and this way is the preferred one, because you don't create unneeded keywords in the process).</p> <p>The latter two forms will be converted to upper-case strings. So a keyword stays a keyword, and a package gets its named as string, converted from that keyword.</p></li> </ul> <p>To sum up, keywords have the value of themselves, as well as any other symbols. The difference is that keywords don't require explicit qualification with <code>keyword</code> package or its explicit usage. And as other symbols they can serve as names for objects. Like, for example, you can name a function with a keyword and it will be "magically" accessible in every package :) See @Xach's <a href="http://xach.livejournal.com/301076.html" rel="nofollow">blogpost</a> for details.</p>
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    1. POHow do keywords work in Common Lisp?
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    1. USVsevolod Dyomkin
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    1. COThank you! `(getf :key-param args)` - is really nice explanation. Also, I tried keyword-named functions, in Lispworks something like `(defun :test () "hi")` causes an error `Defining function :TEST visible from package KEYWORD.` (but there is a debugger option "Define it anyway"), while in SBCL everything works.
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    2. COWelcome! I also have to say, that I've accidentally wrote this in wrong order - the proper way is `(getf args :key-param)` :)
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