diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index cb868a0a06..8048d19d26 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -62,17 +62,17 @@ For inserting text see |insert.txt|.
 :[range]d[elete] [x]	Delete [range] lines (default: current line) [into
 			register x].
 			Note these weird abbreviations:
-			   :dl		delete and list
-			   :dell	idem
-			   :delel	idem
-			   :deletl	idem
-			   :deletel	idem
-			   :dp		delete and print
-			   :dep		idem
-			   :delp	idem
-			   :delep	idem
-			   :deletp	idem
-			   :deletep	idem
+			  :dl		delete and list
+			  :dell		idem
+			  :delel	idem
+			  :deletl	idem
+			  :deletel	idem
+			  :dp		delete and print
+			  :dep		idem
+			  :delp		idem
+			  :delep	idem
+			  :deletp	idem
+			  :deletep	idem
 
 :[range]d[elete] [x] {count}
 			Delete {count} lines, starting with [range]
diff --git a/runtime/doc/tagsrch.txt b/runtime/doc/tagsrch.txt
index 67b2e41fbc..9272d7d613 100644
--- a/runtime/doc/tagsrch.txt
+++ b/runtime/doc/tagsrch.txt
@@ -840,8 +840,8 @@ CTRL-W i		Open a new window, with the cursor on the first line
 			Like `[D`  and `]D`, but search in [range] lines
 			(default: whole file).
 			See |:search-args| for [/] and [!].
-			Note that `:dl` works like `:delete` with the "l"
-			flag, not `:dlist`.
+			Note: `:dl` works like `:delete` with the "l" flag,
+			not `:dlist`.
 
 							*[_CTRL-D*
 [ CTRL-D		Jump to the first macro definition that contains the
diff --git a/runtime/doc/usr_20.txt b/runtime/doc/usr_20.txt
index 51e2ead124..a86053377f 100644
--- a/runtime/doc/usr_20.txt
+++ b/runtime/doc/usr_20.txt
@@ -119,6 +119,14 @@ Some of the ":" commands are really long.  We already mentioned that
 ":substitute" can be abbreviated to ":s".  This is a generic mechanism, all
 ":" commands can be abbreviated.
 
+The builtin function |fullcommand()| can be used to return an abbreviated
+command's full name.  For example, the following commands echo "edit", "echo",
+and "echomsg":
+>vim
+	:echo fullcommand('e')
+	:echo fullcommand('ec')
+	:echo fullcommand('echom')
+<
 How short can a command get?  There are 26 letters, and many more commands.
 For example, ":set" also starts with ":s", but ":s" doesn't start a ":set"
 command.  Instead ":set" can be abbreviated to ":se".
diff --git a/runtime/doc/vimfn.txt b/runtime/doc/vimfn.txt
index 977aca65a3..1a5ba40ca1 100644
--- a/runtime/doc/vimfn.txt
+++ b/runtime/doc/vimfn.txt
@@ -2901,8 +2901,16 @@ fullcommand({name})                                              *fullcommand()*
 		Returns an empty string if a command doesn't exist or if it's
 		ambiguous (for user-defined commands).
 
-		For example `fullcommand('s')`, `fullcommand('sub')`,
-		`fullcommand(':%substitute')` all return "substitute".
+		Note: Command validation is not performed.  Results depend on
+		Vim's internal command-specific identification rules.
+		Examples:
+>vim
+		  echo [fullcommand('s')]		|" ['substitute']
+		  echo [fullcommand('sub')]		|" ['substitute']
+		  echo [fullcommand(': mark word')]	|" ['mark']
+		  echo [fullcommand(': markword')]	|" ['']
+		  echo [fullcommand('en')]		|" ['endif']
+<
 
                 Parameters: ~
                   • {name} (`string`)
diff --git a/runtime/lua/vim/_meta/vimfn.gen.lua b/runtime/lua/vim/_meta/vimfn.gen.lua
index b7184207d2..6b70685a28 100644
--- a/runtime/lua/vim/_meta/vimfn.gen.lua
+++ b/runtime/lua/vim/_meta/vimfn.gen.lua
@@ -2571,8 +2571,16 @@ function vim.fn.foreach(expr1, expr2) end
 --- Returns an empty string if a command doesn't exist or if it's
 --- ambiguous (for user-defined commands).
 ---
---- For example `fullcommand('s')`, `fullcommand('sub')`,
---- `fullcommand(':%substitute')` all return "substitute".
+--- Note: Command validation is not performed.  Results depend on
+--- Vim's internal command-specific identification rules.
+--- Examples:
+--- >vim
+---   echo [fullcommand('s')]    |" ['substitute']
+---   echo [fullcommand('sub')]    |" ['substitute']
+---   echo [fullcommand(': mark word')]  |" ['mark']
+---   echo [fullcommand(': markword')]  |" ['']
+---   echo [fullcommand('en')]    |" ['endif']
+--- <
 ---
 --- @param name string
 --- @return string
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index e4018cc6ea..5728b248e3 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -3230,9 +3230,16 @@ M.funcs = {
       Returns an empty string if a command doesn't exist or if it's
       ambiguous (for user-defined commands).
 
-      For example `fullcommand('s')`, `fullcommand('sub')`,
-      `fullcommand(':%substitute')` all return "substitute".
-
+      Note: Command validation is not performed.  Results depend on
+      Vim's internal command-specific identification rules.
+      Examples:
+      >vim
+        echo [fullcommand('s')]		|" ['substitute']
+        echo [fullcommand('sub')]		|" ['substitute']
+        echo [fullcommand(': mark word')]	|" ['mark']
+        echo [fullcommand(': markword')]	|" ['']
+        echo [fullcommand('en')]		|" ['endif']
+      <
     ]=],
     name = 'fullcommand',
     params = { { 'name', 'string' } },
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 425760f4ec..2a08f635fe 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -3269,6 +3269,14 @@ char *find_ex_command(exarg_T *eap, int *full)
     }
   }
 
+  // Force ":ho" to be unresolved.  Without this, find_ex_command()
+  // matches it to CMD_horizontal (the only "ho*" entry), which makes
+  // fullcommand("ho") return "horizontal" even though ":ho" cannot be
+  // used as the modifier (cmdmods[] requires 3 chars, "hor").
+  if (eap->cmdidx == CMD_horizontal && p - eap->cmd == 2) {
+    eap->cmdidx = CMD_SIZE;
+  }
+
   return p;
 }
 
diff --git a/test/old/testdir/test_marks.vim b/test/old/testdir/test_marks.vim
index 44201cb289..59b7d9757a 100644
--- a/test/old/testdir/test_marks.vim
+++ b/test/old/testdir/test_marks.vim
@@ -253,7 +253,14 @@ func Test_marks_k_cmd()
   call setline(1, ['foo', 'bar', 'baz', 'qux'])
   1,3kr
   call assert_equal([0, 3, 1, 0], getpos("'r"))
+  " whitespace before mark
+  4k f
+  call assert_equal([0, 4, 1, 0], getpos("'f"))
+  :2     k	 g
+  call assert_equal([0, 2, 1, 0], getpos("'g"))
   bw!
+  call assert_fails(':kz7', 'E488: Trailing characters: z7')
+  call assert_fails(':execute ":k^"', 'E191: Argument must be a letter or forward/backward quote')
 endfunc
 
 " Test for file marks (A-Z)
diff --git a/test/old/testdir/test_vimscript.vim b/test/old/testdir/test_vimscript.vim
index 458eae9134..7d7cb7c535 100644
--- a/test/old/testdir/test_vimscript.vim
+++ b/test/old/testdir/test_vimscript.vim
@@ -7620,6 +7620,33 @@ func Test_catch_pattern_trailing_chars()
   bw!
 endfunc
 
+" Test using fullcommand() {{{1
+func Test_builtin_fullcommand()
+  " :hor is the minimum abbreviation of :horizontal; :ho is invalid
+  call assert_equal('', fullcommand('ho'))
+  call assert_equal('horizontal', fullcommand('hor'))
+
+  " :k takes one {a-zA-Z'} mark argument and optional whitespace
+  call assert_equal('k', fullcommand('k'))
+  call assert_equal('k', fullcommand(':k'))
+  call assert_equal('k', fullcommand('karrrrrgh!'))
+
+  " :dl is "delete and list" in a legacy Vim script scope
+  call assert_equal('delete', fullcommand('dl'))
+
+  " :s two and three letter commands
+  call assert_equal('substitute', fullcommand('sIr'))
+  call assert_equal('substitute', fullcommand('sIrarrrrrgh!'))
+
+  " :finally
+  call assert_equal('finally', fullcommand('fina'))
+    " 'final' - returns 'final', a Vim9 script-exclusive keyword
+    "         - is a valid shortening of :finally in legacy Vim script
+    "call assert_equal('final', fullcommand('final'))
+  call assert_equal('finally', fullcommand('finall'))
+
+endfunc
+
 "-------------------------------------------------------------------------------
 " Modelines								    {{{1
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker