Learn Hardcore Japanese: kono miti ha nagai desu.

この is a demonstrative adjective meaning “this.” It directly modifies the following noun (道) to indicate which road you’re talking about. Japanese has three basic demonstratives:

この (this, near the speaker)
その (that, near the listener)
あの (that, away from both)

Why is the particle は used after 道, instead of が?

は is the topic marker, so この道は means “as for this road.” It sets the stage for your comment.

は introduces known information or what you want to talk about.
が marks the grammatical subject, often introducing new or focused information.
Using が here (この道が長いです) would emphasize “this road is the one that’s long,” which shifts the nuance.

What type of word is 長い, and what does it mean?

長い (ながい) is an i-adjective meaning “long.” I-adjectives end with い in their dictionary (plain) form and can directly modify nouns (e.g., 長い道, “a long road”).

Why is です added after 長い?

です is the polite copula used to end sentences politely. Although i-adjectives can stand alone in casual speech (just 長い), appending です (→ 長いです) makes the statement more polite and formal.

What is the basic word order in this Japanese sentence?

Japanese often follows a Topic–Comment structure rather than strict Subject–Verb–Object. Here:
• Topic: この道は (“As for this road…”)
• Comment/Predicate: 長いです (“…is long.”)

Can we omit です, or drop は in casual speech?

Yes.

Dropping です yields この道は長い, which is casual/plain.
Omitting は (if context is clear) gives この道、長いね, a very casual, conversational style (with ね inviting agreement).

Why are there spaces between each word in the example?

Native Japanese writing normally doesn’t use spaces. They’re shown here to help learners identify individual units: この / 道 / は / 長い / です. In real Japanese text, these elements run together without spaces.