Advanced Inference: -나 보다 vs -는가 보다

The logic behind this grammar is simple: Evidence + Conclusion. Imagine you see a friend yawning every five seconds. Your evidence is the yawning. Your conclusion is that they are tired. You'd say, "They must be tired." In Korean, you attach these endings to the verb or adjective stem to show that link. The "evidence" part is the secret sauce here. If you just guess something with zero proof, this grammar feels a bit out of place. It’s like saying "I guess it’s raining" while sitting in a windowless basement with no internet—people might look at you a bit funny! You need that sensory input. Maybe you hear the "pitter-patter" on the roof or see wet pavement. That’s enough! Think of it like a grammar traffic light: the evidence is the green light that allows you to use these endings.

1. 1Let's break down the "how-to" step by step. It's actually easier than assembling IKEA furniture, I promise!
2. 2For Verbs (Present Tense): Take the verb stem and add 나 보다. For example, 먹다 (to eat) becomes 먹나 봐요.
3. 3For Adjectives (Present Tense): This one is a bit pickier. If the stem ends in a vowel, add ㄴ가 보다. 예쁘다 (pretty) becomes 예쁜가 봐요. If it ends in a consonant, add 은가 보다. 작다 (small) becomes 작은가 봐요.
4. 4For Past Tense: Whether it's a verb or an adjective, always use 나 보다 after the past tense marker 았/었/였. So, 갔다 (went) becomes 갔나 봐요 (I guess they went).
5. 5For Nouns: Use Noun + 인가 보다. 학생 (student) becomes 학생인가 봐요.
6. 6For 있다 and 없다: These always behave like verbs and take 나 보다. So, 있나 봐요 (I guess there is) or 없나 봐요 (I guess there isn't).

You’ll find yourself using this in tons of real-world scenarios. Imagine you are at a restaurant and see a guy at the next table turning bright red and drinking gallons of water. You can whisper to your friend, 정말 매운가 봐요! (It must be really spicy!). Or maybe you go to your professor's office and the lights are off. You’d say, 벌써 퇴근했나 봐요 (I guess they already went home). It’s also perfect for social media—if you see a friend's photo of a huge cake, you can comment, 맛있나 봐요! (It looks/must be delicious!). Use it whenever you want to show you are making a logical deduction. It makes you sound engaged with the world around you. It's also a fantastic conversation starter because it invites the other person to confirm or deny your guess.

This is where things can get a little tricky, so pay attention! First, never use this for yourself. You can't say "I guess I am hungry" using 배고픈가 봐요. You *know* if you are hungry! You are the boss of your own feelings. If you use it for yourself, it sounds like you are having an out-of-body experience, which is definitely a bit spooky. Second, don't use it for future guesses where you have absolutely no evidence. If you are just predicting the weather for next month based on nothing, use -(으)ㄹ 것 같다 instead. Third, don't use it for things you've experienced directly in that very moment. If you just took a bite of soup and it's salty, just say "It's salty!" Using 나 봐요 makes it sound like you are guessing based on the color of the soup rather than the actual taste in your mouth.

The biggest trip-up for learners is using the wrong ending for adjectives. Many people accidentally say 비싸나 봐요 (wrong) instead of 비싼가 봐요 (correct). Just remember: Verbs are "Action" so they get the 나 (think of it as "Now" action). Adjectives are "Status" so they get the ㄴ/은. Another classic mistake is the "Self-Guess" we mentioned—avoid it like a bad haircut! Lastly, don't forget the space! In formal writing, it’s 나 (space) 보다. Though in fast texting, people often skip it, keeping the space makes your writing look polished. Yes, even native speakers mess this up sometimes, especially with words like 있다, so don't beat yourself up if you slip up occasionally.

You probably already know -(으)ㄹ 것 같다. How is it different? Think of -(으)ㄹ 것 같다 as a wide umbrella. It covers "I think," "It seems," and "It might." It’s very vague and safe. On the other hand, 나 보다 is the Evidence Specialist. If you say 비가 올 것 같아요, you are saying "I think it will rain" (maybe you just have a gut feeling). If you say 비가 오나 봐요, you are saying "I guess it's raining" because you actually see people with umbrellas or hear thunder. One is based on your internal feeling, while the other is based on external clues. Use 나 보다 when you want to show you've actually noticed something!