ame no hi ni ie de nanimo sinaide iru to, sukosi taikutu de tumaranai.

雨の日 literally means a rain day or more naturally a rainy day.

Here, の links two nouns:

• 雨 = rain
• 日 = day

So 雨の日 means a day of rain / a rainy day.

This is a very common pattern in Japanese:

• 夏の日 = a summer day
• 休みの日 = a day off
• 晴れの日 = a sunny day

In this sentence, 雨の日に means on a rainy day or on rainy days.

The に marks a point or occasion in time.

So:

• 雨の日に = on a rainy day

Japanese often uses に with time expressions when you want to mark when something happens.

In this sentence, it sets the time frame for the rest of the sentence: on a rainy day, if you stay at home and do nothing, it feels boring.

A learner might wonder why it is not は instead. は could also appear in a different version if you wanted to make rainy days the topic, but here に is simply marking the time.

Because で marks the place where an action happens.

• 家で = at home / in the house as the location of the action
• 何もしないでいる is the action/state happening there

So:

• 家で何もしないでいる = to stay at home doing nothing

By contrast, に with a place often marks:

• destination: 家に帰る = go home
• existence: 家にいる = be at home

Here, since the sentence focuses on what you do at home, で is natural.

By itself, 何も literally suggests anything, but with a negative it means nothing.

So:

• 何も + negative verb = nothing / not anything

Examples:

• 何もない = there is nothing
• 何も食べない = eat nothing
• 何もしない = do nothing

In your sentence, the negative is inside しないでいる, so 何も works with that negative:

• 何もしないでいる = to be doing nothing / to stay without doing anything

This is a very common grammar pattern.

This is a very good question, because いる adds an important nuance.

• 何もしない = do nothing
• 何もしないでいる = be in the state of doing nothing, remain without doing anything

So しないでいる emphasizes a continuing state. It is not just one decision not to do something; it suggests sitting there, spending time that way.

In this sentence, that nuance matters:

• 家で何もしないでいると gives the feeling of when you stay at home and just do nothing...

It sounds more natural and descriptive than simply 何もしないと.

No, they are different.

In 家で, で is a particle marking the place of an action.

In しないでいる, the で is part of a grammar pattern:

• V-ないでいる

This means to remain in the state of not doing V.

So:

• 食べないでいる = remain without eating
• 話さないでいる = remain silent / not speak for a while
• 何もしないでいる = remain doing nothing

So even though both are written で, they are doing different jobs.

Here, と is not the and particle.

It is a conditional と, meaning something like:

• when
• if
• whenever

So:

• 家で何もしないでいると、少し退屈でつまらない。
• When/if you stay at home doing nothing, it’s a little boring and dull.

This と is often used for a natural, expected, or general result.

It can sound like:

• Whenever X happens, Y happens
• If you do X, Y is what follows

So the sentence has a general truth feeling: on rainy days, staying home and doing nothing tends to be boring.

They are similar, but not exactly the same.

• 退屈 = bored / boring in the sense of tedious, dull, unstimulating
• つまらない = boring, uninteresting, not enjoyable

So together they reinforce the feeling:

• 退屈でつまらない = boring and dull / tedious and uninteresting

Using both makes the description stronger and more natural than repeating one idea in English with just boring.

Also, note the difference in word type:

• 退屈 is a na-adjective / adjectival noun
• つまらない is an i-adjective

Because で is the connective form of a na-adjective like 退屈.

To connect adjectives in Japanese:

• 静かで広い = quiet and spacious
• 便利で安い = convenient and cheap
• 退屈でつまらない = boring and dull

So the pattern is:

• na-adjective + で + adjective/predicate

Here:

• 退屈で connects to
• つまらない

That is why だ does not appear there.

少し means a little or somewhat.

In this sentence, it softens the judgment:

• 少し退屈でつまらない = a little boring and dull / somewhat boring

It is not necessarily modifying only 退屈 in a strict logical way; in natural interpretation it softens the whole description.

So the overall feeling is:

• it’s not horribly awful
• just kind of boring

The subject is omitted, which is very normal in Japanese.

Depending on context, it could mean:

• I feel this way
• you feel this way
• people in general feel this way

Because of the conditional と, the sentence has a general truth flavor, so it often feels like a broad statement:

• On rainy days, if you stay home and do nothing, it’s a little boring.

But in conversation, it could easily refer to the speaker’s own feeling too:

• When I stay home doing nothing on rainy days, I get a little bored.

Japanese often leaves this unspecified unless the context makes it necessary.

There could be one in other versions, but Japanese often omits は when the sentence is already understandable.

For example, you might also see a version like:

• 雨の日は、家で何もしないでいると、少し退屈でつまらない。

That version makes rainy days the explicit topic.

But the original sentence is still natural. Japanese frequently leaves topic marking unstated when the meaning is clear from context or from the sentence structure itself.

So the lack of は is not a mistake; it just makes the sentence a little more plain and direct.

The comma is mostly for readability and rhythm.

Without the comma, the sentence would still be understandable:

• 雨の日に家で何もしないでいると少し退屈でつまらない。

But the comma helps separate:

• the condition: 雨の日に家で何もしないでいると
• the result: 少し退屈でつまらない

So it makes the sentence easier to read, especially since the first part is fairly long.