diff --git a/Library/Homebrew/manpages/brew.1.md.erb b/Library/Homebrew/manpages/brew.1.md.erb
index aa0c76ce9b..b2ce261cea 100644
--- a/Library/Homebrew/manpages/brew.1.md.erb
+++ b/Library/Homebrew/manpages/brew.1.md.erb
@@ -30,21 +30,25 @@ Linux distribution to your home directory without requiring `sudo`.
 
 ## TERMINOLOGY
 
-**Formula**: The package definition
+**formula**: Homebrew package definition built from upstream sources
 
-**Cask**: An extension of Homebrew to install macOS native apps
+**cask**: Homebrew package definition that installs macOS native applications
 
-**Keg**: The installation prefix of a **Formula**
+**keg**: installation destination directory of a given **formula** version e.g. `/usr/local/Cellar/foo/0.1`
 
-**Keg-only**: A **Formula** is **Keg-only** if it is not linked into the Homebrew prefix
+**rack**: directory containing one or more versioned kegs e.g. `/usr/local/Cellar/foo`
 
-**Cellar**: All **Kegs** are installed here
+**keg-only**: a **formula** is **keg-only** if it is not symlinked into Homebrew's prefix (e.g. `/usr/local`)
 
-**Caskroom**: All **Casks** are installed here
+**cellar**: directory containing one or more named **racks** e.g. `/usr/local/Cellar`
 
-**Tap**: A Git repository of **Formulae** and/or commands
+**Caskroom**: directory containing one or more named **casks** e.g. `/usr/local/Caskroom`
 
-**Bottle**: Pre-built **Keg** used instead of building from source
+**external command**: `brew` subcommand defined outside of the Homebrew/brew GitHub repository
+
+**tap**: directory (and usually Git repository) of **formulae**, **casks** and/or **external commands**
+
+**bottle**: pre-built **keg** poured into the **cellar**/**rack** instead of building from upstream sources
 
 ## ESSENTIAL COMMANDS
 
diff --git a/docs/Manpage.md b/docs/Manpage.md
index 94f216b6c3..e5518f820b 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -14,21 +14,25 @@ Linux distribution to your home directory without requiring `sudo`.
 
 ## TERMINOLOGY
 
-**Formula**: The package definition
+**formula**: Homebrew package definition built from upstream sources
 
-**Cask**: An extension of Homebrew to install macOS native apps
+**cask**: Homebrew package definition that installs macOS native applications
 
-**Keg**: The installation prefix of a **Formula**
+**keg**: installation destination directory of a given **formula** version e.g. `/usr/local/Cellar/foo/0.1`
 
-**Keg-only**: A **Formula** is **Keg-only** if it is not linked into the Homebrew prefix
+**rack**: directory containing one or more versioned kegs e.g. `/usr/local/Cellar/foo`
 
-**Cellar**: All **Kegs** are installed here
+**keg-only**: a **formula** is **keg-only** if it is not symlinked into Homebrew's prefix (e.g. `/usr/local`)
 
-**Caskroom**: All **Casks** are installed here
+**cellar**: directory containing one or more named **racks** e.g. `/usr/local/Cellar`
 
-**Tap**: A Git repository of **Formulae** and/or commands
+**Caskroom**: directory containing one or more named **casks** e.g. `/usr/local/Caskroom`
 
-**Bottle**: Pre-built **Keg** used instead of building from source
+**external command**: `brew` subcommand defined outside of the Homebrew/brew GitHub repository
+
+**tap**: directory (and usually Git repository) of **formulae**, **casks** and/or **external commands**
+
+**bottle**: pre-built **keg** poured into the **cellar**/**rack** instead of building from upstream sources
 
 ## ESSENTIAL COMMANDS
 
diff --git a/manpages/brew.1 b/manpages/brew.1
index a8e6d28e61..7d458a737e 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -16,36 +16,44 @@
 Homebrew is the easiest and most flexible way to install the UNIX tools Apple didn\'t include with macOS\. It can also install software not packaged for your Linux distribution to your home directory without requiring \fBsudo\fR\.
 .
 .SH "TERMINOLOGY"
-\fBFormula\fR
-    The package definition
+\fBformula\fR
+    Homebrew package definition built from upstream sources
 .
 .P
-\fBCask\fR
-    An extension of Homebrew to install macOS native apps
+\fBcask\fR
+    Homebrew package definition that installs macOS native applications
 .
 .P
-\fBKeg\fR
-    The installation prefix of a \fBFormula\fR
+\fBkeg\fR
+    installation destination directory of a given \fBformula\fR version e\.g\. \fB/usr/local/Cellar/foo/0\.1\fR
 .
 .P
-\fBKeg\-only\fR
-    A \fBFormula\fR is \fBKeg\-only\fR if it is not linked into the Homebrew prefix
+\fBrack\fR
+    directory containing one or more versioned kegs e\.g\. \fB/usr/local/Cellar/foo\fR
 .
 .P
-\fBCellar\fR
-    All \fBKegs\fR are installed here
+\fBkeg\-only\fR
+    a \fBformula\fR is \fBkeg\-only\fR if it is not symlinked into Homebrew\'s prefix (e\.g\. \fB/usr/local\fR)
+.
+.P
+\fBcellar\fR
+    directory containing one or more named \fBracks\fR e\.g\. \fB/usr/local/Cellar\fR
 .
 .P
 \fBCaskroom\fR
-    All \fBCasks\fR are installed here
+    directory containing one or more named \fBcasks\fR e\.g\. \fB/usr/local/Caskroom\fR
 .
 .P
-\fBTap\fR
-    A Git repository of \fBFormulae\fR and/or commands
+\fBexternal command\fR
+    \fBbrew\fR subcommand defined outside of the Homebrew/brew GitHub repository
 .
 .P
-\fBBottle\fR
-    Pre\-built \fBKeg\fR used instead of building from source
+\fBtap\fR
+    directory (and usually Git repository) of \fBformulae\fR, \fBcasks\fR and/or \fBexternal commands\fR
+.
+.P
+\fBbottle\fR
+    pre\-built \fBkeg\fR poured into the \fBcellar\fR/\fBrack\fR instead of building from upstream sources
 .
 .SH "ESSENTIAL COMMANDS"
 For the full command list, see the \fICOMMANDS\fR section\.