diff --git a/src/constructor.ts b/src/constructor.ts
index a0bbbfc..7507b8f 100644
--- a/src/constructor.ts
+++ b/src/constructor.ts
@@ -13,8 +13,8 @@ export { constructor as Ono };
 function Ono<T extends ErrorLike>(ErrorConstructor: ErrorLikeConstructor<T>, options?: OnoOptions) {
   options = normalizeOptions(options);
 
-  function ono<E extends ErrorLike, P extends object>(...args: unknown[]) {
-    let { originalError, props, message } = normalizeArgs<E, P>(args, options!);
+  function ono<TError extends ErrorLike, TProps extends object>(...args: unknown[]) {
+    let { originalError, props, message } = normalizeArgs<TError, TProps>(args, options!);
 
     // Create a new error of the specified type
     let newError = new (ErrorConstructor as ErrorLikeConstructorClass<T>)(message);
diff --git a/src/extend-error.ts b/src/extend-error.ts
index 52e0c9b..c80e053 100644
--- a/src/extend-error.ts
+++ b/src/extend-error.ts
@@ -12,8 +12,10 @@ const protectedProps: Array<string | symbol> = ["name", "message", "stack"];
  * @param originalError - The original error object, if any
  * @param props - Additional properties to add, if any
  */
-export function extendError<T extends ErrorLike, E extends ErrorLike, P extends object>(error: T, originalError?: E, props?: P) {
-  let onoError = error as unknown as T & E & P & OnoError<T & E & P>;
+export function extendError<TError extends ErrorLike, TOriginal extends ErrorLike, TProps extends object>(
+  error: TError, originalError?: TOriginal, props?: TProps) {
+
+  let onoError = error as unknown as TError & TOriginal & TProps & OnoError<TError & TOriginal & TProps>;
 
   extendStack(onoError, originalError);
 
diff --git a/src/normalize.ts b/src/normalize.ts
index 2ef85fc..425e2f5 100644
--- a/src/normalize.ts
+++ b/src/normalize.ts
@@ -16,9 +16,9 @@ export function normalizeOptions(options?: OnoOptions): OnoOptions {
 /**
  * Normalizes the Ono arguments, accounting for defaults, options, and optional arguments.
  */
-export function normalizeArgs<E extends ErrorLike, P extends object>(args: unknown[], options: OnoOptions) {
-  let originalError: E | undefined;
-  let props: P | undefined;
+export function normalizeArgs<TError extends ErrorLike, TProps extends object>(args: unknown[], options: OnoOptions) {
+  let originalError: TError | undefined;
+  let props: TProps | undefined;
   let formatArgs: unknown[];
   let message = "";
 
@@ -28,16 +28,16 @@ export function normalizeArgs<E extends ErrorLike, P extends object>(args: unkno
   }
   else if (typeof args[1] === "string") {
     if (args[0] instanceof Error) {
-      originalError = args[0] as E;
+      originalError = args[0] as TError;
     }
     else {
-      props = args[0] as P;
+      props = args[0] as TProps;
     }
     formatArgs = args.slice(1);
   }
   else {
-    originalError = args[0] as E;
-    props = args[1] as P;
+    originalError = args[0] as TError;
+    props = args[1] as TProps;
     formatArgs = args.slice(2);
   }
 
diff --git a/src/singleton.ts b/src/singleton.ts
index b088dca..db72f19 100644
--- a/src/singleton.ts
+++ b/src/singleton.ts
@@ -19,7 +19,7 @@ const onoMap = ono as unknown as Record<string, Ono<Error>>;
  * Creates a new error with the specified message, properties, and/or inner error.
  * If an inner error is provided, then the new error will match its type, if possible.
  */
-function ono<E extends ErrorLike, P extends object>(...args: unknown[]) {
+function ono<TError extends ErrorLike, TProps extends object>(...args: unknown[]) {
   let originalError = args[0] as ErrorLike | undefined;
 
   // Is the first argument an Error-like object?
diff --git a/src/to-json.ts b/src/to-json.ts
index e18db8c..09bab6d 100644
--- a/src/to-json.ts
+++ b/src/to-json.ts
@@ -8,7 +8,7 @@ const objectPrototype = Object.getPrototypeOf({});
  * Custom JSON serializer for Error objects.
  * Returns all built-in error properties, as well as extended properties.
  */
-export function toJSON<E extends ErrorLike>(this: E): ErrorPOJO & E {
+export function toJSON<T extends ErrorLike>(this: T): ErrorPOJO & T {
   // HACK: We have to cast the objects to `any` so we can use symbol indexers.
   // see https://github.com/Microsoft/TypeScript/issues/1863
   let pojo: any = {};
@@ -25,7 +25,7 @@ export function toJSON<E extends ErrorLike>(this: E): ErrorPOJO & E {
     }
   }
 
-  return pojo as ErrorPOJO & E;
+  return pojo as ErrorPOJO & T;
 }
 
 
diff --git a/src/types.ts b/src/types.ts
index 552c74a..1b3a74b 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -24,7 +24,7 @@ export interface OnoConstructor {
    * Returns an object containing all properties of the given Error object,
    * which can be used with `JSON.stringify()`.
    */
-  toJSON<E extends ErrorLike>(error: E): ErrorPOJO & E;
+  toJSON<T extends ErrorLike>(error: T): T & ErrorPOJO;
 
   /**
    * Extends the given Error object with enhanced Ono functionality, such as improved support for
@@ -41,7 +41,7 @@ export interface OnoConstructor {
    * @param error - The error object to extend. This object instance will be modified and returned.
    * @param props - An object whose properties will be added to the error
    */
-  extend<T extends ErrorLike, P extends object>(error: T, props?: P): T & P & OnoError<T & P>;
+  extend<TError extends ErrorLike, TProps extends object>(error: TError, props?: TProps): TError & TProps & OnoError<TError & TProps>;
 
   /**
    * Extends the given Error object with enhanced Ono functionality, such as nested stack traces
@@ -50,7 +50,7 @@ export interface OnoConstructor {
    * @param error - The error object to extend. This object instance will be modified and returned.
    * @param originalError - The original error. This error's stack trace will be added to the error's stack trace.
    */
-  extend<T extends ErrorLike, E extends ErrorLike>(error: T, originalError?: E): T & E & OnoError<T & E>;
+  extend<TError extends ErrorLike, TOriginal extends ErrorLike>(error: TError, originalError?: TOriginal): TError & TOriginal & OnoError<TError & TOriginal>;
 
   /**
    * Extends the given Error object with enhanced Ono functionality, such as nested stack traces,
@@ -60,7 +60,7 @@ export interface OnoConstructor {
    * @param originalError - The original error. This error's stack trace will be added to the error's stack trace.
    * @param props - An object whose properties will be added to the error
    */
-  extend<T extends ErrorLike, E extends ErrorLike, P extends object>(error: T, originalError?: E, props?: P): T & E & P & OnoError<T & E & P>;
+  extend<TError extends ErrorLike, TOriginal extends ErrorLike, TProps extends object>(error: TError, originalError?: TOriginal, props?: TProps): TError & TOriginal & TProps & OnoError<TError & TOriginal & TProps>;
 }
 
 /**
@@ -77,7 +77,7 @@ export interface Ono<T extends ErrorLike> {
    *
    * @param error - The original error
    */
-  <E extends ErrorLike>(error: E): T & E & OnoError<T & E>;
+  <TError extends ErrorLike>(error: TError): T & TError & OnoError<T & TError>;
 
   /**
    * Creates a new error with the message, stack trace, and properties of another error,
@@ -86,7 +86,7 @@ export interface Ono<T extends ErrorLike> {
    * @param error - The original error
    * @param props - An object whose properties will be added to the returned error
    */
-  <E extends ErrorLike, P extends object>(error: E, props: P): T & E & P & OnoError<T & E & P>;
+  <TError extends ErrorLike, TProps extends object>(error: TError, props: TProps): T & TError & TProps & OnoError<T & TError & TProps>;
 
   /**
    * Creates a new error with a formatted message and the stack trace and properties of another error.
@@ -95,7 +95,7 @@ export interface Ono<T extends ErrorLike> {
    * @param message - The new error message, possibly including argument placeholders
    * @param params - Optional arguments to replace the corresponding placeholders in the message
    */
-  <E extends ErrorLike>(error: E, message: string, ...params: unknown[]): T & E & OnoError<T & E>;
+  <TError extends ErrorLike>(error: TError, message: string, ...params: unknown[]): T & TError & OnoError<T & TError>;
 
   /**
    * Creates a new error with a formatted message and the stack trace and properties of another error,
@@ -106,7 +106,7 @@ export interface Ono<T extends ErrorLike> {
    * @param message - The new error message, possibly including argument placeholders
    * @param params - Optional arguments to replace the corresponding placeholders in the message
    */
-  <E extends ErrorLike, P extends object>(error: E, props: P, message: string, ...params: unknown[]): T & E & P & OnoError<T & E & P>;
+  <TError extends ErrorLike, TProps extends object>(error: TError, props: TProps, message: string, ...params: unknown[]): T & TError & TProps & OnoError<T & TError & TProps>;
 
   /**
    * Creates an error with a formatted message.
@@ -121,7 +121,7 @@ export interface Ono<T extends ErrorLike> {
    *
    * @param props - An object whose properties will be added to the returned error
    */
-  <P extends object>(props: P): T & P & OnoError<T & P>;
+  <TProps extends object>(props: TProps): T & TProps & OnoError<T & TProps>;
 
   /**
    * Creates an error with a formatted message and additional properties.
@@ -130,7 +130,7 @@ export interface Ono<T extends ErrorLike> {
    * @param message - The new error message, possibly including argument placeholders
    * @param params - Optional arguments to replace the corresponding placeholders in the message
    */
-  <P extends object>(props: P, message: string, ...params: unknown[]): T & P & OnoError<T & P>;
+  <TProps extends object>(props: TProps, message: string, ...params: unknown[]): T & TProps & OnoError<T & TProps>;
 }
 
 /**