"I know the boy."
Translation:Conozco al niño.
Saber is for knowledge of facts, and conocer is for familiarity with people and places.
It's a concept we call the "a personal". With some verbs, if the (in)direct object is a person, the word is "personified" with the "a".
Incidentally, this also explains, in part, the construction for "gustar" which is usually memorized, and rightly so. It's "A mí me gusta" because the first person is the Indirect Object in Spanish, and is a person. (Since the "mí" is before the verb in that case, there's one more reason to include "a".) You could say "Lo conozco al niño" but "Lo" is unnecessary. If you changed the order of the sentence to emphasize the boy: "Al niño lo conozco", "lo" would suddenly be completely necessary.
tl;dr Because that's how Spanish works.
I put "Lo conozco al niño," and was marked wrong. Why is the "lo" unnecessary?
Simply: Because Spanish speakers don't reduplicate (repeat in different ways) the Direct Object in a typically structured sentence, like they do with an Indirect Object.
A more complex answer would look at the history of the Spanish language and find some time in the evolution of the Vulgar Latin of the Iberian Peninsula when they started reduplicating the Indirect Object but not the Direct Object or something like that, but I don't know that answer.
Perhaps it will help to imagine the following conversation, say between two women: --¡Qué bonito es el pastel de tu hijo! --¡Sí! y Martín se lo compró. --¿¡Martín!? --¿No lo conoces? --Pues sí conozco a Martín, pero ¡Wow! El pastel que Martín le compró a tu Juancito es tan bonito!
Maybe that will help, maybe not, but for me it often helps to see concepts in a context slightly longer than one sentence!
I would like to know the difference between "Conozco al niño" And "Conozco el niño". Both sentences are accepted by duo. Is the second one wrong?
I put "Lo sé al niño." I lost a heart. Two things: 1) The verb "saber" (to know) is irregular, and the first person singular is "yo se." So, I would like to know why "sé" was unacceptable. 2) Why wasn't the pronoun "lo" correct? Is it because a direct object doesn't get the pronoun that precedes the verb? Is this because ONLY the indirect object (that is a noun) gets the pronoun preceding the verb?
I didn't see dejongbrent's comments until after I wrote this. I am still leaving the comment b/c it might help some people understand his comment better.
Saber vs. conocer is an interesting case. Both translate as "to know" but they are not interchangeable; ser vs. estar and por vs. para would be similar cases.
In general, conocer is a deeper knowledge than saber. If you want to say you know a fact, you use saber. If you want to say you know a person, on the other hand, you use conocer. Other things that you can know use one or the other of the verbs based both on what kind of thing they are and how well you know them.
In the past simple (pretérito), both of these verbs have a different translation to English, which might help you keep them straight: "Lo supe ayer" = I found out (about it) yesterday; "Lo conocí ayer" = I met him (or it) yesterday.
Then why is the response 'el conoce mujeres' correct in the other question? There is no 'al'.
Because in this case "él" (notice the accent) is the subject of the sentence. The "personal a" is only for objects.
If you're talking about that it should have been "él conoce a mujeres", this is because the "personal a" is only used with a definite group of people. You can say "él conoce a las mujeres" (definite) or "él conoce mujeres" (indefinite), but not a mixture of both.