diff --git a/lib/fileutils.rb b/lib/fileutils.rb
index c115005..c987909 100644
--- a/lib/fileutils.rb
+++ b/lib/fileutils.rb
@@ -110,7 +110,11 @@ def self.private_module_function(name)   #:nodoc:
   end
 
   #
-  # Returns the name of the current directory.
+  # Returns a string containing the path to the current directory:
+  #
+  #   FileUtils.pwd # => "/rdoc/fileutils"
+  #
+  # FileUtils.getwd is an alias for FileUtils.pwd.
   #
   def pwd
     Dir.pwd
@@ -121,18 +125,36 @@ def pwd
   module_function :getwd
 
   #
-  # Changes the current directory to the directory +dir+.
+  # With no block given,
+  # changes the current directory to the directory
+  # at the path given by +dir+; returns zero:
+  #
+  #   FileUtils.pwd # => "/rdoc/fileutils"
+  #   FileUtils.cd('..')
+  #   FileUtils.pwd # => "/rdoc"
+  #   FileUtils.cd('fileutils')
+  #
+  # With a block given, changes the current directory to the directory
+  # at the path given by +dir+, calls the block with argument +dir+,
+  # and restores the original current directory; returns the block's value:
   #
-  # If this method is called with block, resumes to the previous
-  # working directory after the block execution has finished.
+  #   FileUtils.pwd                                     # => "/rdoc/fileutils"
+  #   FileUtils.cd('..') { |arg| [arg, FileUtils.pwd] } # => ["..", "/rdoc"]
+  #   FileUtils.pwd                                     # => "/rdoc/fileutils"
   #
-  #   FileUtils.cd('/')  # change directory
+  # Keyword arguments:
   #
-  #   FileUtils.cd('/', verbose: true)   # change directory and report it
+  # - <tt>verbose: true</tt> - prints an equivalent command:
   #
-  #   FileUtils.cd('/') do  # change directory
-  #     # ...               # do something
-  #   end                   # return to original directory
+  #     FileUtils.cd('..')
+  #     FileUtils.cd('fileutils')
+  #
+  #   Output:
+  #
+  #     cd ..
+  #     cd fileutils
+  #
+  # FileUtils.chdir is an alias for FileUtils.cd.
   #
   def cd(dir, verbose: nil, &block) # :yield: dir
     fu_output_message "cd #{dir}" if verbose
@@ -146,11 +168,14 @@ def cd(dir, verbose: nil, &block) # :yield: dir
   module_function :chdir
 
   #
-  # Returns true if +new+ is newer than all +old_list+.
-  # Non-existent files are older than any file.
+  # Returns +true+ if the file at path +new+
+  # is newer than all the files at paths in array +old_list+;
+  # +false+ otherwise:
+  #
+  #   FileUtils.uptodate?('Rakefile', ['Gemfile', 'README.md']) # => true
+  #   FileUtils.uptodate?('Gemfile', ['Rakefile', 'README.md']) # => false
   #
-  #   FileUtils.uptodate?('hello.o', %w(hello.c hello.h)) or \
-  #       system 'make hello.o'
+  # A non-existent file is considered to be infinitely old.
   #
   def uptodate?(new, old_list)
     return false unless File.exist?(new)
@@ -170,12 +195,34 @@ def remove_trailing_slash(dir)   #:nodoc:
   private_module_function :remove_trailing_slash
 
   #
-  # Creates one or more directories.
+  # Creates directories at the paths in the given +list+
+  # (an array of strings or a single string);
+  # returns +list+.
+  #
+  # With no keyword arguments, creates a directory at each +path+ in +list+
+  # by calling: <tt>Dir.mkdir(path, mode)</tt>;
+  # see {Dir.mkdir}[https://docs.ruby-lang.org/en/master/Dir.html#method-c-mkdir]:
+  #
+  #   FileUtils.mkdir(%w[tmp0 tmp1]) # => ["tmp0", "tmp1"]
+  #   FileUtils.mkdir('tmp4')        # => ["tmp4"]
+  #
+  # Keyword arguments:
+  #
+  # - <tt>mode: <i>integer</i></tt> - also calls <tt>File.chmod(mode, path)</tt>;
+  #   see {File.chmod}[https://docs.ruby-lang.org/en/master/File.html#method-c-chmod].
+  # - <tt>noop: true</tt> - does not create directories.
+  # - <tt>verbose: true</tt> - prints an equivalent command:
+  #
+  #     FileUtils.mkdir(%w[tmp0 tmp1], verbose: true)
+  #     FileUtils.mkdir(%w[tmp2 tmp3], mode: 0700, verbose: true)
+  #
+  #   Output:
+  #
+  #     mkdir tmp0 tmp1
+  #     mkdir -m 700 tmp2 tmp3
   #
-  #   FileUtils.mkdir 'test'
-  #   FileUtils.mkdir %w(tmp data)
-  #   FileUtils.mkdir 'notexist', noop: true  # Does not really create.
-  #   FileUtils.mkdir 'tmp', mode: 0700
+  # Raises an exception if any path in +list+ points to an existing
+  # file or directory, or if for any reason a directory cannot be created.
   #
   def mkdir(list, mode: nil, noop: nil, verbose: nil)
     list = fu_list(list)