diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5e7716c8..a6933d86 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -121,7 +121,7 @@ All notable changes to this project will be documented in this file. This projec
 
 ### What's Changed
 
-- Fix Plug Mini (US) implimentation
+- Fix Plug Mini (US) implementation
 - Housekeeping and update dependencies
 
 **Full Changelog**: https://github.com/OpenWonderLabs/node-switchbot/compare/v1.4.0...v1.4.1
diff --git a/README.md b/README.md
index 0cff1190..b29eaa50 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ But some functionalities of this module were developed through trial and error.
     - [Moving the arm of the Bot](#moving-the-arm-of-the-bot)
   - [`Switchbot` object](#switchbot-object)
     - [`discover()` method](#discover-method)
-    - [`ondiscover` event handler](#ondiscover-event-hander)
+    - [`ondiscover` event handler](#ondiscover-event-handler)
     - [`startScan()` method](#startscan-method)
     - [`stopScan()` method](#stopscan-method)
     - [`onadvertisement` event handler](#onadvertisement-event-handler)
@@ -117,7 +117,7 @@ const switchbot = new Switchbot();
 (async () => {
   // Start to monitor advertisement packets
   await switchbot.startScan();
-  // Set an event hander
+  // Set an event handler
   switchbot.onadvertisement = (ad) => {
     console.log(JSON.stringify(ad, null, '  '));
   };
@@ -145,7 +145,7 @@ const switchbot = new Switchbot();
 switchbot
   .startScan()
   .then(() => {
-    // Set an event hander
+    // Set an event handler
     switchbot.onadvertisement = (ad) => {
       console.log(JSON.stringify(ad, null, "  "));
     };
diff --git a/src/device.ts b/src/device.ts
index a47caa68..25ef7743 100644
--- a/src/device.ts
+++ b/src/device.ts
@@ -520,7 +520,7 @@ export class SwitchbotDevice {
         reject('READ_TIMEOUT');
       }, this._READ_TIMEOUT_MSEC);
 
-      // Read charcteristic data
+      // Read characteristic data
       char.read((error, buf) => {
         if (timer) {
           clearTimeout(timer);
@@ -543,7 +543,7 @@ export class SwitchbotDevice {
         reject('WRITE_TIMEOUT');
       }, this._WRITE_TIMEOUT_MSEC);
 
-      // write charcteristic data
+      // write characteristic data
       char.write(buf, false, (error) => {
         if (timer) {
           clearTimeout(timer);
diff --git a/src/device/woblindtilt.ts b/src/device/woblindtilt.ts
index a6778e40..58a8e38c 100644
--- a/src/device/woblindtilt.ts
+++ b/src/device/woblindtilt.ts
@@ -68,7 +68,7 @@ export class WoBlindTilt extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target position percentage is incorrent: ' +
+            'The type of target position percentage is incorrect: ' +
             typeof percent,
           ),
         );
@@ -80,7 +80,7 @@ export class WoBlindTilt extends SwitchbotDevice {
       if (typeof mode !== 'number') {
         return new Promise((resolve, reject) => {
           reject(
-            new Error('The type of running mode is incorrent: ' + typeof mode),
+            new Error('The type of running mode is incorrect: ' + typeof mode),
           );
         });
       }
diff --git a/src/device/wobulb.ts b/src/device/wobulb.ts
index e9492a30..8910ff23 100644
--- a/src/device/wobulb.ts
+++ b/src/device/wobulb.ts
@@ -47,7 +47,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target brightness percentage is incorrent: ' +
+            'The type of target brightness percentage is incorrect: ' +
               typeof brightness,
           ),
         );
@@ -69,7 +69,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target color_temperature percentage is incorrent: ' +
+            'The type of target color_temperature percentage is incorrect: ' +
               typeof color_temperature,
           ),
         );
@@ -91,7 +91,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target brightness percentage is incorrent: ' +
+            'The type of target brightness percentage is incorrect: ' +
               typeof brightness,
           ),
         );
@@ -101,7 +101,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target red is incorrent: ' +
+            'The type of target red is incorrect: ' +
               typeof red,
           ),
         );
@@ -111,7 +111,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target green is incorrent: ' +
+            'The type of target green is incorrect: ' +
               typeof green,
           ),
         );
@@ -121,7 +121,7 @@ export class WoBulb extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target blue is incorrent: ' +
+            'The type of target blue is incorrect: ' +
               typeof blue,
           ),
         );
diff --git a/src/device/wocurtain.ts b/src/device/wocurtain.ts
index f2b055ed..6b15a524 100644
--- a/src/device/wocurtain.ts
+++ b/src/device/wocurtain.ts
@@ -12,7 +12,7 @@ export class WoCurtain extends SwitchbotDevice {
    * - Open the curtain
    *
    * [Arguments]
-   * - mode | number | Opetional | runing mode (0x01 = QuietDrift, 0xff = Default)
+   * - mode | number | Optional | runing mode (0x01 = QuietDrift, 0xff = Default)
    *
    * [Return value]
    * - Promise object
@@ -27,7 +27,7 @@ export class WoCurtain extends SwitchbotDevice {
    * - close the curtain
    *
    * [Arguments]
-   * - mode | number | Opetional | runing mode (0x01 = QuietDrift, 0xff = Default)
+   * - mode | number | Optional | runing mode (0x01 = QuietDrift, 0xff = Default)
    *
    * [Return value]
    * - Promise object
@@ -58,7 +58,7 @@ export class WoCurtain extends SwitchbotDevice {
    *
    * [Arguments]
    * - percent | number | Required  | the percentage of target position
-   * - mode    | number | Opetional | runing mode (0x01 = QuietDrift, 0xff = Default)
+   * - mode    | number | Optional | runing mode (0x01 = QuietDrift, 0xff = Default)
    *
    * [Return value]
    * - Promise object
diff --git a/src/device/wostrip.ts b/src/device/wostrip.ts
index dd131cbf..d0b4e237 100644
--- a/src/device/wostrip.ts
+++ b/src/device/wostrip.ts
@@ -43,7 +43,7 @@ export class WoStrip extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target brightness percentage is incorrent: ' +
+            'The type of target brightness percentage is incorrect: ' +
               typeof brightness,
           ),
         );
@@ -81,7 +81,7 @@ export class WoStrip extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target brightness percentage is incorrent: ' +
+            'The type of target brightness percentage is incorrect: ' +
               typeof brightness,
           ),
         );
@@ -91,7 +91,7 @@ export class WoStrip extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target red is incorrent: ' +
+            'The type of target red is incorrect: ' +
               typeof red,
           ),
         );
@@ -101,7 +101,7 @@ export class WoStrip extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target green is incorrent: ' +
+            'The type of target green is incorrect: ' +
               typeof green,
           ),
         );
@@ -111,7 +111,7 @@ export class WoStrip extends SwitchbotDevice {
       return new Promise((resolve, reject) => {
         reject(
           new Error(
-            'The type of target blue is incorrent: ' +
+            'The type of target blue is incorrect: ' +
               typeof blue,
           ),
         );
diff --git a/src/parameter-checker.ts b/src/parameter-checker.ts
index 81770ae5..baf94db9 100644
--- a/src/parameter-checker.ts
+++ b/src/parameter-checker.ts
@@ -41,7 +41,7 @@ export class ParameterChecker {
    * [Arguments]
    * - obj      | Object  | Required | Object including parameters you want to check
    * - rules    | Object  | Required | Object including rules for the parameters
-   * - required | Boolean | Optional | Flag whther the `obj` is required or not.
+   * - required | Boolean | Optional | Flag whether the `obj` is required or not.
    *            |         |          | The default is `false`
    *
    * [Return value]
diff --git a/src/switchbot.ts b/src/switchbot.ts
index c7de78fd..61fea801 100644
--- a/src/switchbot.ts
+++ b/src/switchbot.ts
@@ -249,7 +249,7 @@ export class SwitchBot {
             return;
           default:
             err = new Error(
-              'Uknown state: ' + this.noble.state,
+              'Unknown state: ' + this.noble.state,
             );
             reject(err);
             return;