- Of is a preposition that indicates relationships between other words, such as belonging, things made of other things, things that contain other things, or a point of reckoning.
- Off is usually used as an adverb or a preposition. In both cases, it indicates separation or disconnection.
Mixing them up is always a mistake, but of and off are commonly confused nonetheless. Below, we’ve listed some common situations where you want to use of and some where off is the correct choice.
When to Use Of
We use of when we want to show that people or things relate to other things or people. For example, when we want to say that something or someone belongs to or is a part of something or someone else, we can do it like this:
We can also use of to say that something consists of something else, or that it contains something else:
When we want to give a position in space or time, we might use of to link the position with a reference we already know:
Of could be used when we create a noun phrase from a verb phrase:
When to Use Off
Off is the opposite of on:
Off can also be used when we want to say that something is away from a place:
We can use off when we want to say that something has been removed:
from Grammarly Blog https://www.grammarly.com/blog/of-vs-off/