Merge pull request #168 from Zebreus/master

Fixed minor typos in 04

pills/04-basics-of-language.xml

@@ -19,7 +19,7 @@
     <link xlink:href="http://nixos.org/nix/manual/#chap-writing-nix-expressions">Nix language</link>
     is used to write expressions that produce derivations. The
     <link xlink:href="http://nixos.org/nix/manual/#sec-nix-build">nix-build</link>
-    tool is used to build a derivations from an expression. Even as a system administrator that
+    tool is used to build derivations from an expression. Even as a system administrator that
     wants to customize the installation, it's necessary to master Nix. Using
     Nix for your jobs means you get the features we saw in the previous articles
     for free.
@@ -338,7 +338,7 @@
     <title>Laziness</title>
 
     <para>
-      Nix evaluates expression only when needed. This is a great feature when
+      Nix evaluates expressions only when needed. This is a great feature when
       working with packages.
     </para>