Almost any part of a sentence can be omitted if it is understood from context, except the verb.

Every well-formed Japanese sentence has a verb, no exceptions.

The verb always goes last.

Hiragana Romaji Meaning
です desu is/are/am (present)
でした deshita was (past)
では ありません dewa arimasen isn’t/aren’t/am not (present)
では ありません でした dewa arimasen deshita wasn’t (past)

Some examples of the verb to be in English are:

In these examples, the copula took three different forms. That’s because in English, there is a rule called the subject-verb agreement. The verb has to match the subject.

Japanese does not make this distinction. In Japanese, all three above sentences would take the same exact verb form.

りんご です。 “It is an apple”

Japanese has no words for a, an, or the. They do not exist in Japanese, we just add them into our English translation as appropriate to make it sound natural.

What is an apple? In this sentence, that is open for interpretation. In Japanese, you don’t need to specify parts of a sentence that are already already understood from context.

りんご です can be interpreted as: [The thing we understand from context] is [an] apple.

There are also no singular or plurals for most words in Japanese. りんご can be one or multiple apples.

English has a few words like this, such as deer. In Japanese, all nouns work this way.

Therefore, りんご です can also mean: [They] are apples.

Essentially,