Welcome to the World of Relative Clauses!

In this chapter, we are going to learn a special way to describe things and people. You already know how to use relative clauses (like "The dog that is barking"), but today we are looking at something a bit more professional: Prepositions before relative pronouns.

Learning this will help you sound more formal in your writing and much clearer when you are describing complex ideas in subjects like Science, History, or Geography!

Quick Review: What are they?
Prepositions are words that show relationships, like: in, on, at, with, for, about, and from.
Relative Pronouns are words that start relative clauses, like: who, whom, which, and whose.

1. Moving the Preposition: Informal vs. Formal

In everyday English, we often put the preposition at the very end of the sentence. This is informal. In formal writing (like a school report or a science project), we often move that preposition to the front, right before the relative pronoun.

Informal Example:
Science is a subject which I am interested in.

Formal Example (The "Front-loaded" version):
Science is a subject in which I am interested.

Analogy:
Think of the informal version as wearing a t-shirt and jeans to a party. It’s comfortable and everyone understands you. Think of the formal version (putting the preposition first) as wearing a school uniform or a suit. It’s for "official" business!

Key Takeaway: Moving the preposition before the relative pronoun makes your English sound more precise and academic.

2. The "Whom" Rule for People

When we describe people informally, we use who. However, a very important rule in English is that when a preposition comes before the pronoun for a person, we must change who to whom.

Don't worry if this seems tricky! Just remember: if there is a preposition first, use the one with the "m" at the end.

Informal:
The teacher who I spoke to was very helpful.

Formal:
The teacher to whom I spoke was very helpful.

Memory Trick:
Preposition + Whom (Both can end in a consonant sound). You would never say "to who" in a formal essay!

3. Using "Which" for Objects and Ideas

When we are describing objects (like tools in Technology class or chemicals in Science), we use which after the preposition.

Real-World Example (Science/SE):
The test tube in which the liquid is held must be clean.

Real-World Example (History/PSHE):
The era about which we are learning was full of changes.

Key Takeaway: Use Whom for people and Which for things when the preposition comes first.

4. Common Mistake: The "That" Trap

Here is a rule you must never forget: You cannot use the word "that" immediately after a preposition.

Wrong: The house in that I live... (This sounds very strange to an English speaker!)
Right: The house in which I live...

Quick Review Box:
• In which = Correct!
• To whom = Correct!
• With that = Incorrect! (When used as a relative clause)

5. Step-by-Step: How to Join Sentences

If you have two sentences and want to join them using a formal relative clause, follow these steps:

Step 1: Look at the two sentences.
1. This is the pen. 2. I wrote the essay with it.

Step 2: Find the preposition and the object.
The preposition is with. The object is it (the pen).

Step 3: Replace the object with a relative pronoun (which for things).
Change "it" to which.

Step 4: Move the preposition to the front of the relative clause.
This is the pen with which I wrote the essay.

6. Summary and Final Tips

Key Point 1: Putting prepositions before relative pronouns is used for describing things in a formal way.
Key Point 2: Always use whom for people and which for things after a preposition.
Key Point 3: Avoid using that after a preposition in these clauses.

Did you know?
In many non-language subjects like Science (SE) and Mathematics (ME), your textbooks use these formal relative clauses to give very exact definitions. For example: "Osmosis is the process by which molecules pass through a membrane." By learning this, you are actually becoming better at Science and Math too!

Don't be afraid to practice! Start by identifying prepositions in your reading, and soon you will be using to whom and in which like a pro.