hosyoukikan ha itinen desu.

It is read:

ほしょうきかん は いちねん です
Romanization: hoshō kikan wa ichinen desu

Notes:

• 保証期間 = ほしょうきかん
• は is written ha but pronounced wa here
• 一年 = いちねん
• です = desu

In normal writing, it is usually written without spaces:

保証期間は一年です。

保証期間 is a compound noun meaning warranty period or guarantee period.

It is made of:

• 保証 = warranty, guarantee
• 期間 = period, term, length of time

So together, 保証期間 means the period during which the product is covered by the warranty.

This is one of the most common beginner questions in Japanese.

When は is used as a topic particle, it is pronounced wa, not ha.

So in this sentence:

• written: 保証期間は一年です
• spoken: ほしょうきかん wa いちねんです

This is just a standard rule of Japanese grammar. The spelling stays は, but the pronunciation changes when it marks the topic.

は marks the topic of the sentence.

So:

• 保証期間は = as for the warranty period
• 一年です = it is one year

A very literal breakdown is:

• 保証期間 = warranty period
• は = topic marker
• 一年 = one year
• です = polite copula, roughly is

So the sentence structure is basically:

As for the warranty period, it is one year.

That is why the natural English translation becomes The warranty period is one year.

Because 一年 is the predicate noun here.

In a sentence like:

A は B です

the pattern is:

• A = topic
• B = what A is
• です = polite ending

So in:

保証期間は一年です

• 保証期間 = topic
• 一年 = what it is
• です = polite copula

You do not need a particle after 一年 in this pattern.

です makes the sentence polite and completes the statement.

It works like a polite is / am / are in many beginner-level explanations, though it does not function exactly like English to be in every situation.

Here:

• 一年です = is one year

Without です, the sentence would sound less polite or more abrupt:

• 保証期間は一年。

That might appear in ads, labels, or very casual shorthand, but です is the standard polite form for learners to use.

Japanese uses special native counters and time words for many common expressions.

For years in the sense of duration or age, 年 is used.

So:

• 一年 = one year
• 二年 = two years
• 三年 = three years

You do not use 一つ年 for this.

Here, 一年 means a period of one year.

Here it means one year in length.

That is because 一年 can mean different things depending on context:

• one year / a year
• first year, in some contexts such as school level

But in 保証期間は一年です, the meaning is clearly the warranty period is one year long.

If the context were school, 一年 could mean first-year student or first year, but not here.

Yes, absolutely.

一年 and 一年間 can both work here.

Difference:

• 一年 = one year
• 一年間 = for a period of one year, one-year duration

So:

• 保証期間は一年です
• 保証期間は一年間です

Both are natural.
一年間 makes the idea of duration a little more explicit.

In normal Japanese writing, you would write it as 一年 with no space.

Japanese normally does not use spaces between words the way English does.

So:

• normal: 保証期間は一年です。
• spaced version: 保証期間　は　一年　です。

The spaced version is often only used in teaching materials to make the parts easier for beginners to see.

Yes. 1年 is very common, especially in practical writing such as:

• product descriptions
• advertisements
• manuals
• forms

So these are both fine:

• 保証期間は一年です。
• 保証期間は1年です。

Using kanji numbers like 一 can look a little more formal or standard in some contexts, but both are normal.

Because 保証期間 is a standard noun compound.

Japanese often combines nouns directly to make a new noun:

• 保証
  • 期間 → 保証期間

This is similar to English compounds like:

• school year
• warranty period
• train station

You do not need の when the two nouns form a fixed compound like this.

If you used の, it would sound less like a set term and more like a descriptive phrase. In many cases, the compound form is the normal one.

It is polite neutral.

Because it ends in です, it is polite enough for:

• customers
• workplace conversation
• product explanations
• general everyday polite speech

It is not especially formal or stiff, but it is not casual either.

Compare:

• polite: 保証期間は一年です。
• plain/casual: 保証期間は一年だ。
• very blunt shorthand: 保証期間は一年。

For most learners, です is the safest choice.

Yes. That is a very good literal translation.

A natural English translation would usually be:

• The warranty period is one year.
• The warranty lasts for one year.

The literal version helps you understand the grammar:

• 保証期間は = as for the warranty period
• 一年です = is one year

So the literal translation is useful for learning, even if it sounds less natural in English.