Learn Hardcore Japanese: watasi ha sukosi yasumitai desu.

Japanese often omits the subject when it is obvious from context. If it is clear that you are talking about yourself, 少し休みたいです by itself is perfectly fine and common.

You would keep 私 if:

You are explicitly contrasting yourself with others:
- みんなはまだ働きたいですが、私は少し休みたいです。
Or if it is not clear who wants to rest and you need to specify.

What exactly does 休みたい mean, grammatically?

休みたい is the want to rest form of the verb 休む (to rest).

Formation:

Dictionary form: 休む (to rest)
Verb stem: 休み
Add たい: 休みたい

So it is literally rest + want → want to rest.

Grammatically, たい behaves like an i-adjective:

休みたい (want to rest)
休みたくない (do not want to rest)
休みたかった (wanted to rest), etc.

Why is it 休みたいです and not 休みたいます?

Because たい is not a verb ending like ます; it is an i‑adjective attached to the verb stem.

Structure:

Verb stem (休み) + たい (want) → 休みたい (plain form)
To make it polite, you add です, just as with any i‑adjective:
- さむい → さむいです
- たかい → たかいです
- 休みたい → 休みたいです

So 休みたいます is grammatically wrong. You either say:

Plain: 休みたい
Polite: 休みたいです

Can I use 休みたいです to talk about what someone else wants, like He wants to rest?

You normally do not use the たい form to assert another person’s inner desire in statements.

休みたいです is most natural for:
- Your own desire: I want to rest
- Or questions about the listener: 休みたいですか。 (Do you want to rest?)

To talk about a third person’s desire, Japanese usually uses 〜たがっている:

彼は少し休みたがっています。
= He seems to want to rest a little.

This shows that you are observing their behavior rather than claiming to know their inner feelings directly.

What does 少し mean here, and what does it modify?

少し (すこし) means a little / a bit / a short time / a small amount.

In this sentence it works as an adverb, modifying the verb phrase 休みたい:

少し休みたい = I want to rest a little / I want to take a short rest.

It does not mean you want only a small part of something; it is about the amount or duration of the resting.

What is the difference between 少し and ちょっと in this kind of sentence?

Both can often be translated as a little / a bit, and both are fine here.

少し休みたいです。
ちょっと休みたいです。

Differences in nuance:

少し
- Slightly more neutral or textbook‑like.
- Common in both speech and writing.
ちょっと
- Very common in everyday conversation.
- Often used in softening refusals or complaints:
  - 今日はちょっと疲れました。 (I’m a bit tired today.)
- Can sometimes sound a bit more colloquial.

In this simple sentence, you can treat them as almost interchangeable; ちょっと is what you will hear very often in casual speech.

Can I change the word order, like 私は休みたい少しです?

No, that word order is incorrect.

In Japanese, adverbs like 少し normally come before the verb or verb phrase they modify:

Natural:
- 私は少し休みたいです。
- 少し休みたいです。 (with 私 omitted)
Unnatural / wrong:
- 私は休みたい少しです。

The usual pattern is:

[Topic / subject] + [adverbs etc.] + [verb / たい‑form] + です

Can I say 私が少し休みたいです instead? What is the difference from 私は少し休みたいです?

You can say 私が少し休みたいです, but the nuance is different.

私は少し休みたいです。
- Neutral.
- Just stating your desire: As for me, I want to rest a little.
私が少し休みたいです。
- Emphasizes 私 as the one who wants to rest.
- Often used in contrast, like:
  - みんなはまだ働きたいですが、私が少し休みたいです。
    = Everyone else wants to keep working, but I (specifically) want to rest a bit.

If you are simply saying I want to rest a little, 私は… (or just omitting 私) is more normal.

How polite is 私は少し休みたいです。 and what would a casual version look like?

This sentence is polite but not overly formal. It is suited to:

Talking to coworkers
Talking to people you are not very close to
Many everyday situations where polite Japanese is expected

Casual versions:

少し休みたい。
Or, more conversational:
- ちょっと休みたい。
- 少し休みたいんだけど。 (softening / hinting: I kinda want to rest a bit though…)

Dropping です and 私 makes the sentence casual.

How do I say don’t want to rest, wanted to rest, or do you want to rest? with this pattern?

Since 休みたい is an i‑adjective–like form, you conjugate the たい part.

Negative (don’t want to rest)
- Plain: 休みたくない
- Polite: 休みたくないです。
Past (wanted to rest)
- Plain: 休みたかった。
- Polite: 休みたかったです。
Question (Do you want to rest a little?)
- 少し休みたいですか。
- More casual: 少し休みたい？ / ちょっと休みたい？

So the pattern is:

〜たい → 〜たくない (negative)
〜たい → 〜たかった (past)

Why is it 休みたい and not 休むたい?

Because the たい‑form always attaches to the verb stem, not the dictionary form.

For 休む:

Dictionary form: 休む
Verb stem: 休み (remove む, add み)
Add たい to the stem: 休みたい

Other examples:

食べる → stem 食べ → 食べたい (want to eat)
行く → stem 行き → 行きたい (want to go)
読む → stem 読み → 読みたい (want to read)

So 休むたい is incorrect; it must be 休みたい.

How do you pronounce 少し and 休みたい?

少し is read すこし.
休みたい is read やすみたい.

Syllable by syllable:

少し → す・こ・し (su ko shi)
休みたい → や・す・み・た・い (ya su mi ta i)

In natural speech, the たい at the end is usually pronounced clearly, since it carries the want to meaning.