Learn Hardcore Japanese: kono kamera ha itinen no hosyou ga aru kara ansin da. - This camera has a one-year warranty, so I feel at ease.

は marks the topic: “as for this camera…”
が marks the grammatical subject of existence: the thing that “exists” is 保証 (the warranty).
This is a common pattern with ある: Topic(は) + Subject(が) + ある.
If you wanted to strongly emphasize which camera has the warranty, you’d restructure: 一年の保証があるのはこのカメラだ (The one that has a one-year warranty is this camera).

What does の do in 一年の保証? Can I say 一年間の保証 or 一年保証 instead?

の links nouns: “a warranty of one year” (genitive/attributive link).
一年の保証 and 一年間の保証 are both natural; 一年間 emphasizes the span a bit more and is common in formal writing.
一年保証 (no の) is a set phrase often used in ads/spec sheets; it’s more label-like/compact.
Numerals are fine too: 1年の保証 / 1年間の保証.

Why is it ある and not いる?

ある is for inanimate or abstract things that exist/are available (a warranty, a plan, a meeting).
いる is for animate beings (people, animals).
A warranty is not a living thing, so 保証がある is correct.

Can I say このカメラには一年の保証がある? What’s the nuance of には?

Yes. X には Y がある is a very common “X has Y” pattern.
このカメラは一年の保証がある is also fine; には can make the possession relation clearer and can add slight contrast/emphasis.
Another natural option for products is 一年の保証がついている (“comes with a one-year warranty”).

How does から work here? Do I need plain forms before から?

から marks a reason/cause: Reason + から, Result.
Use the form that matches your overall politeness:
- Plain: 一年の保証があるから安心だ。
- Polite: 一年の保証がありますから安心です。
Keep the style consistent across the sentence; don’t mix plain and polite haphazardly.

What’s the difference between から and ので?

Both mean “because,” but:
- ので sounds softer/more objective and is a bit more formal.
- から is more direct/personal and common in conversation.
Polite examples:
- 一年の保証があるので安心です。
- For nouns/na-adjectives before ので, use なので (e.g., 便利なので).

Can I put the reason first: 一年の保証があるから、このカメラは安心だ?

Yes. Reason-first is very natural. You can repeat or omit the topic after the comma:
- 一年の保証があるから、このカメラは安心だ。
- 一年の保証があるから、安心だ。

What exactly is 安心? Why 安心だ and not 安心する or 安心できる?

安心 is a noun/na-adjective.
- 安心だ = “(it’s) reassuring / (I’m) at ease” (state/evaluation).
- 安心する = “to feel relieved” (an action/response).
- 安心できる = “can feel at ease” (potential/ability; often natural with reasons).
All can work with slightly different nuance:
- 保証があるから安心だ。 (It’s reassuring.)
- 保証があるから安心する。 (I feel relieved.)
- 保証があるから安心できる。 (I can be at ease.)

Does 安心だ describe the camera or my feeling?

Pragmatically, it expresses the speaker’s or general people’s feeling/evaluation: “That’s reassuring.”
Japanese often omits the person who feels it; context supplies it.
If you want to describe the product as physically safe, use 安全だ. 安心な can modify nouns (e.g., 安心なサービス), but for devices 安全な or expressions about reliability are more common.

Why end with だ? Could it be です? How do I make the whole sentence polite?

だ is the plain copula for nouns/na-adjectives; です is the polite form.
Polite version of the whole sentence:
- このカメラには一年間の保証がありますので、安心です。
- or このカメラには一年間の保証がありますから、安心です。

Can I use だから instead of から here?

Not directly after a verb/adjective clause. だから attaches to nouns/na-adjectives or starts a new sentence.
Use から after verbs/adjectives: 保証があるから安心だ.
To use だから, split it: 一年の保証がある。だから、安心だ。
With a noun/na-adjective as the reason, you can use だから: 保証は一年だから安心だ。

How do you read the key words?

What’s the difference among 保証, 保障, and 補償?

保証 (guarantee/warranty): a promise of quality or repair/replacement within a period. Used here.
保障 (security/assurance): protection of rights or safety (e.g., 人権保障).
補償 (compensation): monetary/material compensation for loss or damage.
Memory tip: 補 (to supplement/compensate) → 補償 is money; 保 (to protect) + 証 (proof) → 保証 is a proof-backed promise.

Are spaces between words normal in Japanese?

No. Spaces are added in learner materials. Normally it’s written without spaces:
- このカメラは一年の保証があるから安心だ。

Is あるですから wrong?