Zero Conditional: When vs If

Imagine a simple rule. If you heat ice, it melts. This isn't a guess about the future. It is a fact of nature. This is what the Zero Conditional does. It connects a condition to a guaranteed result. You aren't talking about one specific time. You are talking about *any* time the condition is met. Think of it like a computer program. "If input A happens, execute result B." It is very logical. Native speakers use it to sound certain. If you want to explain how a machine works, use this. If you want to describe your cat's annoying habits, use this too. It feels modern because it is direct. No "maybe," no "might," just facts. It is the grammar of truth. Even native speakers mess this up by adding will, but you won't. You are keeping it simple and present.

1. 1Building this is easier than assembling IKEA furniture. You only need the Present Simple. You use it in both parts of the sentence.
2. 2Start with if or when. This is your trigger.
3. 3Add the condition using the Present Simple. If you drink coffee late...
4. 4Add a comma if you started with if or when. It is a tiny pause.
5. 5End with the result using the Present Simple. ...you don't sleep well.
6. 6You can also flip the sentence. You don't sleep well if you drink coffee late. See? No comma needed when the if is in the middle. It's like a grammar traffic light. Green means go, red means stop for a comma. Just remember: keep both sides in the present. Do not let will sneak in. It belongs in the First Conditional, not here.

Use the Zero Conditional when something is a universal truth. Science is a great place for this. If you mix red and blue, you get purple. It also works for personal habits. When I wake up, I check my phone. (Yes, we all do it). Use it for instructions or rules at work. If the alarm rings, leave the building. It is perfect for job interviews when describing your skills. When I face a problem, I stay calm. It shows you are consistent. Use when if you are sure the condition happens often. Use if if the condition is just a possibility. If you're at a restaurant: If I eat peanuts, I get sick. This is a vital rule for your health! It’s all about things that are always or generally true.

Don't use this for specific future plans. If you are talking about tomorrow's lunch, use the First Conditional. If I go to that cafe tomorrow, I will buy a sandwich. That is a one-time thing. The Zero Conditional is for *every* time. Also, don't use it for the past. If you are telling a story about your childhood, use the past tense. Another trap is using it for things that are only "maybe" true. This grammar is for certainties. If there is a chance the result won't happen, you need a different pattern. Think of it like a scientific law. If the law can be broken, the Zero Conditional is probably the wrong choice. Keep it for the "always" moments.

The biggest mistake is adding will to the result. If it rains, the grass will get wet. That sounds okay, but for a general fact, we say the grass gets wet. Another common slip is the comma. If the if clause comes first, you MUST have a comma. If you are late, call me. Without it, the sentence feels like a long run-on sentence. Also, watch your subject-verb agreement. Remember the -s for he, she, and it. When she exercises, she feels better. People often forget that -s when focusing on the logic. Finally, don't confuse if and when. While similar, when implies it definitely happens. If implies it might happen. Don't say when for things that are rare or lucky, like winning the lottery!

Let's look at the First Conditional. It uses will. If I see him, I will tell him. This is for a specific event. The Zero Conditional is If I see him, I say hello. This means you *always* say hello every time you see him. See the difference? One is a specific plan; the other is a habit. Then there is when vs if. When it rains, I take an umbrella. This means it rains often, and this is my routine. If it rains, I take an umbrella. This means *on the condition* that it rains, I do this. When is for certainty and frequency. If is for the condition itself. They are close, but when feels more like a schedule.