diff --git a/src/elements.rs b/src/elements.rs
index d4c29ff3..ea307aff 100644
--- a/src/elements.rs
+++ b/src/elements.rs
@@ -7,5 +7,6 @@ pub mod pipeline;
 pub mod command;
 pub mod io;
 pub mod word;
+pub mod subword;
 
 use self::io::pipe::Pipe;
diff --git a/src/elements/subword.rs b/src/elements/subword.rs
new file mode 100644
index 00000000..6aca362e
--- /dev/null
+++ b/src/elements/subword.rs
@@ -0,0 +1,26 @@
+//SPDX-FileCopyrightText: 2022 Ryuichi Ueda ryuichiueda@gmail.com
+//SPDX-License-Identifier: BSD-3-Clause
+
+pub mod unquoted;
+pub mod brace;
+
+use crate::{Feeder, ShellCore};
+use super::subword::unquoted::UnquotedSubword;
+use std::fmt;
+use std::fmt::Debug;
+
+impl Debug for dyn Subword {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct(&self.get_text()).finish()
+    }
+}
+
+pub trait Subword {
+    fn get_text(&self) -> String;
+    fn eval(&mut self) -> Vec<Vec<String>>;
+}
+
+pub fn parse(feeder: &mut Feeder, core: &mut ShellCore) -> Option<Box<dyn Subword>> {
+    if let Some(a) = UnquotedSubword::parse(feeder, core){ Some(Box::new(a)) }
+    else{ None }
+}
diff --git a/src/elements/word.rs b/src/elements/word.rs
index 3fbdb7f9..c2d8a4e6 100644
--- a/src/elements/word.rs
+++ b/src/elements/word.rs
@@ -2,6 +2,8 @@
 //SPDX-License-Identifier: BSD-3-Clause
 
 use crate::{Feeder, ShellCore};
+use crate::elements::subword;
+use crate::elements::subword::Subword;
 
 #[derive(Debug)]
 pub struct Word {