Substitution (Pro-forms)

We use substitution to avoid repeating words we already know. It is all about efficiency. When you and your friend both know what you are talking about, you don't need the full name of the object anymore. You replace the noun with one or ones. You can also replace whole actions with do. It is like a grammar magic trick. You take a big, heavy phrase and turn it into a tiny, light word. This keeps the listener focused on the new information. For example, if you are talking about cars, the important part is that the new car is red, not that it is a car again. By using one, you highlight the color. It is a simple switch that makes you sound much more advanced than a beginner.

1. 1Identify the noun or action you want to avoid repeating.
2. 2Check if the noun is singular (just one thing) or plural (many things).
3. 3For a singular noun, use the word one. Example: "The big one."
4. 4For plural nouns, use the word ones. Example: "The blue ones."
5. 5For an action (verb), use the helper verb do, does, or did. Example: "I play tennis and he does too."
6. 6For a whole thought or sentence, use so or not. Example: "I think so."

• Shopping for clothes: This is the most common place to use it. "I like this shirt, but I prefer that green one."
• Ordering food: If your friend gets a pizza, you can say, "I'll have a small one too."
• Comparing things: When looking at two phones, you might say, "The expensive one is better."
• Answering questions: Instead of repeating the whole question, just use a pro-form. "Do you like coffee?" "I do."
• Job interviews: To sound professional and concise. "I haven't finished the report, but I plan to do so by five o'clock."

• The first mention: Never use substitution before you have said the real noun. If you walk up to a stranger and say "I like that one," they will think you are a bit strange. Mention the car or dog first!
• Uncountable nouns: You cannot use one for things like water, rice, or money. You can't say "I want the cold water one." Just say "I want the cold water."
• After possessives alone: We usually don't say "This is my one." We just say "This is mine." However, you can say "This is my new one" if you add an adjective.
• Very formal documents: In some legal papers, they repeat the noun to be 100% clear. But for 99% of your life, use substitution!

• Mixing up One and It: This is the big one. Think of it like a grammar traffic light. Use it for the exact same object. Use one for a different object of the same type. If you lose your phone, you look for it. If you want a new phone, you buy one.
• Forgetting the Plural: Many people say "I like those blue one." Remember, if there are two or more, you must use ones.
• Using with 'Some': We don't usually say "I have some ones." We just say "I have some." It sounds much more natural to leave the word out entirely there.
• Using 'One' for people incorrectly: You can use it for people ("The tall one"), but don't use it if you are being very polite or formal. Use "The tall gentleman" instead.

• Substitution vs. Omission: Sometimes we just delete the word. "Do you want a drink?" "Yes, I'd love one" (Substitution). "Do you want a drink?" "Yes, I'd love to" (Omission of the verb). Substitution always puts a little "placeholder" word in the gap.
• One vs. A/An: A is for any random thing. One is specifically used when we are choosing between options or avoiding repetition. "I need a pen" (any pen). "I like the blue one" (that specific type).