diff --git a/src/abstract.ts b/src/abstract.ts
new file mode 100644
index 0000000..ee9dc5e
--- /dev/null
+++ b/src/abstract.ts
@@ -0,0 +1,8 @@
+import { Opaque } from "type-fest"
+
+
+export type AbstractTag = "@thilawyn/traitify-ts/Abstract"
+
+export function abstract<Abstract extends object = {}>() {
+    return {} as Opaque<Abstract, AbstractTag>
+}
diff --git a/src/expresses.ts b/src/expresses.ts
index ecdcf4e..5b67030 100644
--- a/src/expresses.ts
+++ b/src/expresses.ts
@@ -1,9 +1,19 @@
 import { Call, Pipe, Tuples } from "hotscript"
-import { AbstractClass, Opaque } from "type-fest"
-import { Trait, TraitAbstractMembersFn, TraitApplierSuperTag, TraitImplClassFn, TraitImplInstanceFn } from "."
+import { AbstractClass, Class, Opaque } from "type-fest"
+import { AbstractTag, Trait, TraitAbstractMembersFn, TraitApplierSuperTag, TraitImplClassFn, TraitImplInstanceFn } from "."
 import { ExtendFn, ExtendableFn, SimplifyFn, StaticMembersFn } from "./util"
 
 
+type SubtraitApplier<
+    Traits           extends Trait<any, any>[],
+    Abstract         extends object,
+    ImplWithAbstract extends Class<Abstract, []>,
+> = (
+    (Super: Opaque<AbstractClass<Abstract>, TraitApplierSuperTag>) => (
+        Opaque<ImplWithAbstract, TraitApplierSuperTag>
+    )
+)
+
 class TraitExpression<
     Super  extends AbstractClass<any>,
     Traits extends Trait<any, any>[],
@@ -40,6 +50,22 @@ class TraitExpression<
             this.superclass as Opaque<Super, TraitApplierSuperTag>,
         ) as any
     }
+
+    subtrait<
+        SubtraitAbstract extends object,
+        SubtraitImpl     extends Class<any>,
+    >(
+        abstract: (
+            abstract: Pipe<Traits, [
+                Tuples.Map<TraitAbstractMembersFn>,
+                SimplifyFn,
+            ]>
+        ) => Opaque<SubtraitAbstract, AbstractTag>,
+
+        // impl: ()
+    ) {
+
+    }
 }
 
 export type Implements<Exp extends TraitExpression<any, any>> = (
diff --git a/src/index.ts b/src/index.ts
index ae86066..b839462 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,2 +1,3 @@
+export * from "./abstract"
 export * from "./expresses"
 export * from "./trait"