Nouns are a fundamental building block of the language and allow us to talk about a person, thing, concept, or place.
As mentioned in the lesson about verbs, every valid sentence needs to contain at least 1 verb (although it can be implied), but does not require nouns. Without using nouns, the sentences we can form a bit limited, so most sentences contain at least 1 noun.
Let's look at an example:
There is a mountain.
In the above sentence, 山 is the noun meaning "mountain" and だ expresses the state of being, literally meaning the mountain exists, but it can have a different meaning depending on the context.
There are no articles equivalent to "a" and "an" in Japanese, nouns can be used directly which makes things simpler in some ways. Nouns are also not conjugated, meaning it's only necessary to learn a single form and use it in every situation.
A logical question is then, how do we transform the previous question into plural (expressing that there are several mountains)?
There are mountains.
As you might have noticed, the sentence didn't change at all, so how can we know if the sentence is talking about a single mountain or multiple mountains?
As with many other things in Japanese, it depends on the context.
Without knowing the full conversation the sentence was used in, it is impossible to imply whether the sentence is talking about a single mountain or multiple mountains.
There also exists the pluralizing suffix 達 which can appear at the end of certain words to specifically indicate the plural, for example 人 can mean a single person or multiple people, but 人たち can only mean multiple people. We cannot simply attach this suffix to arbitrary words as it can only be used with specific words.
Here are some common nouns that you can start studying ahead of time if you like:
For more words check out the words page.