These words sound the same, but a sensor is a device, a censor is a person who cuts potentially offensive material from a text or broadcast, and a censer is a container for incense.

A sensor is a device that detects motion, light, smoke, or even speed. If you have a smoke detector in your home, you’re familiar with a sensor — the sensor in the smoke detector “senses” smoke and emits an alarm. (If you don’t have a smoke detector in your home, go get one!) Sensor is related to the word sensory.

We sense you might want some examples:

The architects also added a computer-generated lighting system to alter the mood with light sensors that track the changing weather, seasons and hours of the day. (New York Times)

The retina at the back of eye contains light sensors called cones. (BBC)

A censor might make sure all the “bad” words in a movie are bleeped out or cut scenes of violence from a novel being adapted for young readers. Censor is also a verb, so you might censor yourself when your parents want to know exactly what you said that made your grandmother so angry. Here are more examples:

The struggle over online speech in Russia has important ramifications because the internet companies have been seen as shields from government censors. (New York Times)

China has censored any mention of the event online. (Seattle Times)

Censer, the rarest of the three words, is a holder for incense used in a religious ritual. In the Catholic Church, a priest or an altar server swings a censer during a service; it looks kind of like a smoky small metal pot held by chains. Here are two examples:

Dried and crushed resins of all three plants smolder in a nearby censer, filling the air with heavenly smells of fruity freshness. (Reuters)

The air was stale without a swinging censer. (New York Times)

Because these words sound alike, you may simply have to memorize their distinct spellings. Remember, a sensor senses, a censor cuts offensive material, and a censer holds incense.