diff --git a/docs/glossary.md b/docs/glossary.md
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+++ b/docs/glossary.md
@@ -0,0 +1,93 @@
+(glossary)=
+
+# Glossary
+
+```{currentmodule} click
+```
+
+This glossary defines key terms as they are used throughout the Click
+documentation. It allows us to be internally consistent in our usage.
+
+```{glossary}
+Argument
+    A positional parameter passed to a command. Arguments are defined with
+    the {func}`argument` decorator or the {class}`Argument` class. Unlike
+    options, arguments are positional and do not have names prefixed with
+    dashes. See {doc}`arguments`.
+
+Callback
+    A function that is invoked when a command is executed. In Click, the
+    decorated function itself is the command's callback. Parameter
+    callbacks are invoked when a parameter value is resolved.
+
+Command
+    A single action in a CLI application. Commands are defined using the
+    {func}`command` decorator or the {class}`Command` class. A command
+    accepts parameters (options and arguments) and executes a callback
+    when invoked.
+
+Command Line Application
+    A program that is operated through a terminal by typing text commands.
+    Click is a toolkit for building command line applications in Python.
+
+Command Line Utility
+    A command line application designed to perform a specific task, often
+    as part of a larger workflow. Examples include `pip`, `git`, and
+    `black`.
+
+Context
+    An object that holds state during the execution of a Click command.
+    The {class}`Context` carries information such as the parent context
+    (for nested commands), whether to run in standalone mode, and other
+    invocation metadata. Accessed via {func}`get_current_context` or the
+    `ctx` parameter.
+
+Decorator
+    A Python function that wraps another function. Click uses decorators
+    such as {func}`command`, {func}`option`, {func}`argument`, and
+    {func}`group` to declare CLI parameters and structure.
+
+Environment Variable
+    A value set in the operating system's environment that Click can read
+    as a default for a parameter. Both options and arguments can be
+    configured to pull values from environment variables.
+
+Flag
+    A boolean option that is either present or absent on the command line.
+    Flags do not take a value argument. For example, `--verbose` is a
+    flag. In Click, flags are created by setting `is_flag=True` on an
+    option, or by using {func}`option` with `flag_value`.
+
+Group
+    A command that contains subcommands. Groups are defined using the
+    {func}`group` decorator or the {class}`Group` class. They allow
+    building multi-command CLI applications with nested command structures.
+
+Parameter
+    A generic term covering both {term}`options <Option>` and
+    {term}`arguments <Argument>`. Parameters are the values a user passes
+    to a command. In Click, all parameters are instances of the
+    {class}`Parameter` class.
+
+Option
+    A named parameter prefixed with one or two dashes (e.g., `--name` or
+    `-n`). Options are defined with the {func}`option` decorator or the
+    {class}`Option` class. They can take values, act as {term}`flags`,
+    and accept various configuration such as defaults, types, and
+    environment variable names. See {doc}`options`.
+
+Parameter Type
+    The type of a parameter's value, such as `str`, `int`, `float`, or a
+    custom {class}`ParamType`. Click uses parameter types to validate and
+    convert input. See {doc}`parameter-types`.
+
+Subcommand
+    A command that is nested inside a {term}`Group`. Subcommands are
+    added to a group using {meth}`Group.add_command` or the
+    {func}`group` decorator's lazy loading features.
+
+Terminal
+    The text-based interface through which a user interacts with a
+    command line application. Also referred to as a console, shell, or
+    command prompt. Click applications read input from and write output
+    to the terminal.
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diff --git a/docs/index.rst b/docs/index.rst
index c496e59c5f..f6efa5cf68 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -118,6 +118,7 @@ General Reference
    command-line-reference
    unicode-support
    wincmd
+   glossary
 
 API Reference
 -------------------
@@ -142,4 +143,4 @@ About Project
    contributing
    contrib
    license
-   changes
+   changes
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