"고양이는 음식이 아닙니다."
Translation:A cat is not food.
Keep in mind that the verb "is" is like an equal sign. In English the subject is placed before the verb and a predicate nominative that refers to the subject is placed after the verb. In some languages, both nouns may be considered as if they were both subjects. In Chinese, one of these will be marked as the topic.
Subject(subject or topic marker) Predicate Nominative(subject or topic marker) (negative,if needed) verb
고양이는 음식이 아닙니다.
So the word order is as if they wrote: cat food not is
Yet there is an extra syllable attached to the end of each noun that marks which is the topic and which is just another subject (or in my mind I think of it as equal to the subject). Also, keep in mind that in another sentence you may find that an object is marked as the topic.
고양이 (cat) 는 (topic marker for words that end in a vowel)
음식 (food) 이 (subject marker for words that end in a consonant)
아 (this is what is negating the verb)
It is from 아니 which means "no".
닙니다 (this is the verb, here "is"; remember the verb doesn't conjugate as it does in English, so it looks the same for "am" and "are")
Here is the link for the skill set Basics1 which explains in more detail this Korean grammar, just scroll down to read the tips and notes with an internet browser.) https://www.duolingo.com/skill/ko/basics-1
Now you would click on the skill and click on the lightbulb icon for the tips and notes.
The plural marker may or may not be used. The general statement "Cats are not food." is equivalent to "A cat is not food." It all depends on whether they are trying to teach you the plural marker. When you do see that plural marker, you won't have the choice any more to translate it as singular.
No. In this sentence 고양이 has a 는 ending, indicating topic case, while 음식 gets an 이 ending indicating nominative case. -를 and -을 indicate accusative case. The verb in this case is 있다, meaning to be.
Usually, subject case indicates the actor of a sentence while the accusative is the target of the action. But the verb be and 있다 are used to state that two things are the same. With this verb, there is no target of the action, so this never has an accusative (no 를 or 을). Most languages with grammatical case would have both the cat and the food as nominative case. In Korean, the first is topic case, and the second is nominative.