diff --git a/homeassistant/components/binary_sensor/hikvision.py b/homeassistant/components/binary_sensor/hikvision.py
index e87fcb7980..f9ff4ac0a7 100644
--- a/homeassistant/components/binary_sensor/hikvision.py
+++ b/homeassistant/components/binary_sensor/hikvision.py
@@ -214,7 +214,7 @@ class HikvisionBinarySensor(BinarySensorDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._id
 
     @property
diff --git a/homeassistant/components/juicenet.py b/homeassistant/components/juicenet.py
index 728a4fccf8..55567d4587 100644
--- a/homeassistant/components/juicenet.py
+++ b/homeassistant/components/juicenet.py
@@ -70,5 +70,5 @@ class JuicenetDevice(Entity):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return "{}-{}".format(self.device.id(), self.type)
diff --git a/homeassistant/components/media_player/apple_tv.py b/homeassistant/components/media_player/apple_tv.py
index c2c7098473..4c5145ce1a 100644
--- a/homeassistant/components/media_player/apple_tv.py
+++ b/homeassistant/components/media_player/apple_tv.py
@@ -79,7 +79,7 @@ class AppleTvDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self.atv.metadata.device_id
 
     @property
diff --git a/homeassistant/components/media_player/cast.py b/homeassistant/components/media_player/cast.py
index 635951590a..dbcb53ec18 100644
--- a/homeassistant/components/media_player/cast.py
+++ b/homeassistant/components/media_player/cast.py
@@ -418,7 +418,7 @@ class CastDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self) -> str:
-        """Return an unique ID."""
+        """Return a unique ID."""
         if self.cast.uuid is not None:
             return str(self.cast.uuid)
         return None
diff --git a/homeassistant/components/media_player/openhome.py b/homeassistant/components/media_player/openhome.py
index bca6f2ad77..5e30f9783c 100644
--- a/homeassistant/components/media_player/openhome.py
+++ b/homeassistant/components/media_player/openhome.py
@@ -156,7 +156,7 @@ class OpenhomeDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._device.Uuid()
 
     @property
diff --git a/homeassistant/components/media_player/songpal.py b/homeassistant/components/media_player/songpal.py
index 83637633ba..b1dc7df331 100644
--- a/homeassistant/components/media_player/songpal.py
+++ b/homeassistant/components/media_player/songpal.py
@@ -128,7 +128,7 @@ class SongpalDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._sysinfo.macAddr
 
     @property
diff --git a/homeassistant/components/media_player/sonos.py b/homeassistant/components/media_player/sonos.py
index 5928122dba..0ba0c89081 100644
--- a/homeassistant/components/media_player/sonos.py
+++ b/homeassistant/components/media_player/sonos.py
@@ -367,7 +367,7 @@ class SonosDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._unique_id
 
     @property
diff --git a/homeassistant/components/media_player/squeezebox.py b/homeassistant/components/media_player/squeezebox.py
index 1fd61b3ead..86b4087ca8 100644
--- a/homeassistant/components/media_player/squeezebox.py
+++ b/homeassistant/components/media_player/squeezebox.py
@@ -230,7 +230,7 @@ class SqueezeBoxDevice(MediaPlayerDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._id
 
     @property
diff --git a/homeassistant/components/remote/apple_tv.py b/homeassistant/components/remote/apple_tv.py
index 36eee4b284..7d11c931a6 100644
--- a/homeassistant/components/remote/apple_tv.py
+++ b/homeassistant/components/remote/apple_tv.py
@@ -45,7 +45,7 @@ class AppleTVRemote(remote.RemoteDevice):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._atv.metadata.device_id
 
     @property
diff --git a/homeassistant/components/sensor/tibber.py b/homeassistant/components/sensor/tibber.py
index 2e82d98af2..5ce614b978 100644
--- a/homeassistant/components/sensor/tibber.py
+++ b/homeassistant/components/sensor/tibber.py
@@ -106,6 +106,6 @@ class TibberSensor(Entity):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         home = self._tibber_home.info['viewer']['home']
         return home['meteringPointData']['consumptionEan']
diff --git a/homeassistant/components/xiaomi_aqara.py b/homeassistant/components/xiaomi_aqara.py
index 96f10de68e..b6e04d867f 100644
--- a/homeassistant/components/xiaomi_aqara.py
+++ b/homeassistant/components/xiaomi_aqara.py
@@ -242,7 +242,7 @@ class XiaomiDevice(Entity):
 
     @property
     def unique_id(self) -> str:
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._unique_id
 
     @property
diff --git a/homeassistant/components/zha/__init__.py b/homeassistant/components/zha/__init__.py
index 9a8c88e6f2..88ca29101a 100644
--- a/homeassistant/components/zha/__init__.py
+++ b/homeassistant/components/zha/__init__.py
@@ -306,7 +306,7 @@ class Entity(entity.Entity):
 
     @property
     def unique_id(self) -> str:
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._unique_id
 
     @property
diff --git a/homeassistant/components/zwave/__init__.py b/homeassistant/components/zwave/__init__.py
index 0149bb9287..21db39d4e7 100644
--- a/homeassistant/components/zwave/__init__.py
+++ b/homeassistant/components/zwave/__init__.py
@@ -916,7 +916,7 @@ class ZWaveDeviceEntity(ZWaveBaseEntity):
 
     @property
     def unique_id(self):
-        """Return an unique ID."""
+        """Return a unique ID."""
         return self._unique_id
 
     @property
diff --git a/homeassistant/helpers/entity.py b/homeassistant/helpers/entity.py
index a3c6e7a944..f23a49c185 100644
--- a/homeassistant/helpers/entity.py
+++ b/homeassistant/helpers/entity.py
@@ -93,7 +93,7 @@ class Entity(object):
 
     @property
     def unique_id(self) -> str:
-        """Return an unique ID."""
+        """Return a unique ID."""
         return None
 
     @property