Difference between ‘in’ and ‘on’
In English grammar we come across these two terms in most instances. They belong to the preposition class and are entirely used to describe the noun in giving the location of that noun. They give the location of an individual or something in relation to an object or period.
Let us take a lively example to illustrate these two prepositions and their usage. The first one is “the laptop is on the desk” and the second to illustrate the usage of in is “the pen is in the bag”. Both words in the above example are used to show the location of something in relation to another object. They communicate different locations when closely examined.
In is used to show that something is inside or within that object that is referred to. In our case above then it simply means that the pen is inside the bag. This conveys clearly the location of the pen to be inside the bag.
The second case in our example the word on is used to show that the laptop is at the top of the desk. These two prepositions therefore communicate differently when used in describing nouns. The behind them is that they are both used to convey the location of an object relative to another.
Same applies when these two terms are used to describe the time. On time and in time, on time simply means that the person reached earlier before the start of an occasion whereas in time means he/she reached the occasion exactly the time that was set.
Both these prepositions ‘in’ and ‘at’ are used in English grammar to give different meaning in terms of location. They give distinctive meanings when especially mixed with other English language verbs. But the idea behind these two words is that they both convey the message of location of an object.