In vs. On: Grammar Rules

in vs onThe use of prepositions, both in the written word as well as verbally, can be tricky whether you are learning the English language or trying to boost your existing English grammar skills. Even very experienced writers may find themselves misusing a preposition if they aren’t paying careful attention. When it comes to in vs. on, you may think the application is simple, but in certain situations, you may be misusing the word.

As the bedrock of communication, grammar skills are a must for any person, and taking the time to learn the proper usage is well worth your time. Visit Udemy for tips and tricks on how to speak better English, and even if you feel your skills are completely lacking, you can always start with an introductory English grammar course to build a solid foundation to start from. Beginners in structured English grammar lessons may also want to check out this course on the elements of grammar.


When using the on preposition in a sentence, there are various situations that might call for it. Typically, you use on whenever you want to denote the position for surfaces or a position just above or outside an area. For instance, whenever setting something on the surface of something: I set a pencil on my desk, or the cup is on the table.

You might also use on when referring to a device or machine. When someone is on the phone, for example, this indicates a person is using the phone. Although this is an idiomatic phrase that makes little sense when taken literally, on is the correct preposition in this instance. Likewise, someone could also be “on the computer” or “on TV” in the event that someone you recognized was being seen on your TV screen. This wouldn’t mean that they were physically sitting on the TV, and in wouldn’t be the right preposition in this case either, as that would imply they were actually inside the television.

On could also be a reference to a part of the body. As an example, you may might say a flung rock struck you on the shoulder, or that you witnessed someone slap someone on the cheek. When someone gets engaged, she wears a ring on her finger.

Another usage for on could involve the state of something. If a building bursts into flames, you would describe it as being “on fire.” Likewise, if you’re out shopping for clothes and there is an item that is half off, you might say that item is “on sale.”


When using in, you’re typically talking about something contained in an object, or something that is inside. Usually it references something that is in a position with space limitations.

It may also be used to represent general times of the day, month, year, or season. For instance, if you say that you tend to wake up early in the morning, or that you work less in the summer, or that your next semester of school starts in August.

In can work when referring to a location or place as well. If you’re traveling, you might be staying in a motel, or if you’re at home, your residence may be in New York. This location does not necessarily have to be a physical place, however. If someone shouts loudly in your ear, or if you are staring directly in the eyes, these are also places that the in preposition works for.

It’s also correct to use in when discussing shape, color or size. When looking at a painting at a museum, you might say that it was done mostly in yellow. Perhaps a group of spectators gathered around an unusual event and formed a ring around the perimeter. This would be the spectators gathering in a circle. When it comes to size, think of clothing. If you’re describing whether a shirt is available in large or medium, you’ll need to rely on the in preposition.

Lastly, in could also be used to describe a belief, opinion, or interest. For instance, you might believe in donating to charities on a regular basis, or have no interest in politics.

Simple grammar mistakes are common, and nearly everyone is guilty of making them from time to time. If you have a good grasp of English grammar but want to brush up on your skills, there are courses at Udemy geared towards the more advanced concepts of English grammar. Check them out to begin improving your skills right away. Once you’ve got a handle on the basics, you may choose to boost your overall English writing skills with Udemy’s Quality Paragraph and Essay Writing course, which is great whether you’re entering into school or taking a position in the world of business. Good grammar is a big help in many ways – knowing the basics, such as in vs. on, is a good place to start.