Spanish expressions: No sé si / que

spanish expressions no se si que

Spanish speakers use the phrases no sé si and no sé qué when they want to express doubts or when something is uncertain for them. We relate these phrases with the verb and adverb no sé. For the same reason, they have similarities between them. The phrase “no sé” gives them their main meaning, although Spanish-speaking individuals use them in different ways.


In this article, you’ll learn how to use and differentiate the phrases no sé si and no sé qué. Thus, expressing doubts or uncertainty will become easier and more comfortable. Besides, using these structures will help you sound like a well-spoken Spanish speaker.


How to use no sé si


First, to explain how to use no sé si, we need to break it down word by word. When we speak of no sé we say that it is the combination of a negation word (no) and the verb saber (to know). Then, we conjugate it using the 1st person indicative.

When it’s time to use no sé si, you must remember that it has to be with an accent mark or tilde. Writing or saying no sé si without an accent mark would be incorrect. On a side, no sé works as a negation statement unit because it is made up of two words.


At this point, you probably are wondering what’s the main purpose of using “no sé si” in a sentence. We all know the meaning of the word si (yes). After all, we often use it in affirmative statements or when we need to say something possible. Nevertheless, in this case, it is a little different.


The word “si” in the phrase “no sé si” works as conditional conjunction. We use it when we want to explain events that will happen in the future. It can also serve as a connector between no sé and the complement of the sentence.


We will use no sé si when we want to deny our knowledge about something or when we have little knowledge about something. It has a similar meaning to the English phrase “I don’t know if”. Let’s see a few examples.


No se si me dará tiempo de llegar a la reunión. / I don’t know if I’ll have time to get to the meeting.


No se si este sea el lugar que decía en la dirección. / I don’t know if this is the place it said in the address.


Todavía no se si podemos confiar en él. / I still don’t know if we can trust him.


How to use no sé qué


No sé qué is the Spanish expression for I do not know what. This phrase is always written separately, even when it has a noun value. We must put no sé que together with other elements that complete its meaning. These elements can be a verb, a subject, or a direct object complement. We can also use no sé qué when we want to refer to “a certain something”. When we use no sé qué in that way, we talk about not knowing a specific thing. Let’s see some examples below,


Yo no sé qué me estaba diciendo. / I don’t know what he was telling me.


No sé qué habrá pasado entre ellos que al final terminaron su relación. / I don’t know what happened between them that, in the end, they ended their relationship.


No sé qué tipo de presentimiento tengo, pero siento que es algo bueno. / I don’t know what kind of feeling I have, but I feel like it is a good thing.


As you can see, we can use no sé qué as a masculine noun when we can not explain a feeling or sensation. Therefore, we can also use it when we can not label something. For example,


Cuando la ví por primera vez, sentí un no sé qué que me dejó paralizado. / When I saw her for the first time, I felt an I don’t know what that left me paralyzed.


Finally, we use no sé que as a phrase to express doubt. For example,


No sé qué le falta a la pintura, necesito algo que la haga brillar. / I do not know what the painting is missing. I need something to make it shine.


No sé si vs no sé qué


In Spanish, we use no sé si and no sé qué when we have doubts. We also use them when we do not have information or don’t know about situations, things, or circumstances. No sé si and no sé qué have similar meanings because both use the Spanish “no sé…”. However, as you’ve seen, we use them in different ways.


One of the biggest differences between no sé si and no sé qué is that when we use no sé qué we talk about more specific things. On the other hand, we can use no sé si, we use it in a more general way. Another difference is that we can use no sé si to add information to the sentence, while with no sé qué, we can’t do that.


You can use no sé si in several ways, while we can rarely use no sé qué in other structures. Let’s see a few examples to see their differences.


No sé si podré ir al cine mañana contigo. / I do not know if I can go to the movies tomorrow with you.


No sé qué usar para la fiesta de hoy. / I do not know what to wear to the party today.


No sé si el señor Jesus pueda esperar tanto tiempo. / I do not know if Mr. Jesus can wait that long.


No sé qué me estaba cayendo mal en el estómago. / I do not know what was going wrong in my stomach.


In conclusion, although there are still people using no sé si and no sé qué for the exact same purposes, you must know it’s not always like that. Of course, they both help us express doubt but the way we say things is completely different. Besides, using no se qué as a noun is common in Latin American countries. So, if you want to add a pretty native-speaker expression to your vocabulary, you will indeed say sometimes “tiene un no se qué”.

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