これはつくえではありません。
- This is not a desk.

これはつくえではありません。 meaning: This is not a desk.

⚫︎ The basic sentence structure in Japanese is Subject-Object-Verb (SOV), but it can sometimes seem flexible. ⚫︎ The subject is often indicated by the particle は(wa), which marks the topic of the sentence. ⚫︎ In this sentence, これ(kore) (this) is the topic, and は(wa) marks it as such. ⚫︎ The subject doesn't always have to be explicitly stated. It can be implied from context.

⚫︎ は(wa) is a topic marker, indicating what the sentence is about. It comes after the subject. ⚫︎ The word つくえ(tsukue) (desk) is the noun in this sentence. ⚫︎ です(desu) is a polite copula (linking verb), meaning "is" or "are." ⚫︎ To make a sentence negative, you change です(desu) to ではありません(dewa arimasen) or じゃありません(ja arimasen). Both have the same meaning. ⚫︎ Therefore, the sentence pattern is: Subject + は(wa) + Noun + ではありません(dewa arimasen).

⚫︎ In this sentence, the noun is つくえ(tsukue) (desk). ⚫︎ The particle は(wa) indicates that the speaker is talking *about* the desk (or rather, *not* about the desk). ⚫︎ This particle acts to highlight つくえ(tsukue) and to separate the topic from the rest of the sentence.

⚫︎ これ(kore) means "this" and is a demonstrative pronoun. It refers to something close to the speaker. ⚫︎ Demonstrative pronouns are important for identifying things. ⚫︎ Other demonstrative pronouns at the N5 level are それ(sore) (that, near the listener) and あれ(are) (that over there, away from both speaker and listener).

⚫︎ ではありません(dewa arimasen) is the formal negative form of the copula です(desu). ⚫︎ じゃありません(ja arimasen) is a more casual version of the same negative copula, and they are fully interchangeable. ⚫︎ They are fixed expressions, meaning they are always used in the same way to indicate that something *is not* something else. ⚫︎ This contrasts with a positive sentence like これはつくえです。(Kore wa tsukue desu.) which means "This is a desk."