Saying what something is: だ, です and negatives

The first predicate to learn is the one that means "is": it ties a noun to a description or another noun. Japanese has two forms of it, and the difference is politeness, not meaning.

です is the polite form. だ is the plain form, the one you use with friends, family, and inside your own head. You will see だ in casual speech, in novel narration, and in most subtitles of casual dialogue. You will see です with strangers, in shops, on the news, and in many learner materials.

A plain だ at the end of a statement often sounds blunt or emphatic, which is why Japanese people frequently leave it off in casual speech (just 猫。 or 猫ね。). You will also hear it dropped before sentence-ending particles. We will come back to that.

Unlike English "X is Y", the "is" comes after what it describes, just like every other predicate.

That last one shows something useful: です is not just "is". It is a general "this is the case" linker, and English sometimes needs a different verb to say the same thing. Do not expect every だ/です to translate as "is".

To say "is not", you add じゃない (plain) or じゃありません (polite):

じゃ is a slurred form of では, which you will see in writing and in formal speech: ではない, ではありません. They mean the same.

The past of だ is だった; the past of です is でした. For "was not" you attach the past tense to the negative:

One thing that surprises English speakers: you do not put だ in front of a noun to describe it. Instead you attach a linker (の for nouns, な for a certain kind of adjective). You will meet this properly in the lessons on の and adjectives. For now just notice that だ/です only ever closes a sentence; it does not sit in the middle.

Near-everywhere. Names tell you who someone is:

Shop signs, titles, definitions, subtitles: all です and だ. And in novels, the narrator often ends sentences with だ or だった to state facts plainly.

A paragraph of definitions uses だ and です over and over, joined by other words. Read for the pattern: noun + copula, with descriptions stacked in front.

Now a conversation, plain and polite mixed:

• だ is plain "is", です is polite "is". Meaning is the same.
• Negative: じゃない / じゃありません (written: ではない / ではありません).
• Past: だった / でした, past negative: じゃなかった / じゃありませんでした.
• It always comes at the end of what it closes, never before the noun.
• Do not translate every です as "is". Treat it as "this is the case".