sigoto ga owattara, tosyokan ni yoru tumori desu.

In 仕事が終わったら, が marks 仕事 as the thing that finishes.

• 仕事が終わる = work ends / work is finished
• Here, 仕事 is the subject of 終わる

Using は is also possible in some contexts, but it would add a stronger topic or contrast feeling. In this sentence, が is the most natural neutral choice.

So:

• 仕事が終わったら = when work is finished / when I finish work

This is a very common question. In Japanese, the た-form + ら pattern is used to mean when or if something happens.

So:

• 終わった = finished
• 終わったら = when it finishes / when it’s finished

Even though 終わった looks past, 終わったら does not necessarily mean the whole sentence is in the past. It marks one action as happening before the next one.

So the sequence is:

1. work finishes
2. then I plan to stop by the library

〜たら is a conditional form. It can often mean:

• if
• when
• after

In this sentence, 仕事が終わったら is most naturally understood as:

• when work is over
• after work ends

Because finishing work is expected to happen, when/after sounds more natural than if in English.

Because つもりです attaches to the plain form of a verb.

Pattern:

• dictionary form + つもりです = intend to do
• ない-form + つもりです = intend not to do

So:

• 寄る = to stop by
• 寄るつもりです = I intend to stop by

This is why you do not say 寄りますつもりです.

つもりです means intend to or plan to.

So:

• 図書館に寄るつもりです = I intend to stop by the library
• or more naturally, I’m planning to stop by the library

It expresses the speaker’s intention. It is a little more deliberate than just saying what you will do.

Compare:

• 図書館に寄ります = I’ll stop by the library
• 図書館に寄るつもりです = I plan to stop by the library / I intend to stop by the library

With 寄る, the particle に marks the place you stop by.

• 図書館に寄る = stop by the library

Here, に indicates the destination or target place of the stopping-by action.

You can think of it as similar to:

• 家に帰る = go home
• 店に行く = go to the store

So in this sentence, 図書館に means at/to the library in the sense of stopping there.

Not exactly. 寄る means to stop by, drop in, or make a quick visit somewhere on the way.

So:

• 図書館に寄る is not just go to the library
• it suggests stopping by the library, often as an extra stop

That nuance is important. If you simply wanted to say go to the library, you would more likely use 行く.

Compare:

• 図書館に行く = go to the library
• 図書館に寄る = stop by the library

Yes. Japanese often omits subjects when they are clear from context.

So the sentence does not explicitly say:

• 私は

But the meaning is understood as something like:

• When work is over, I plan to stop by the library.

Japanese very often leaves out I, you, he, she, etc. if the listener can infer them.

です makes the sentence polite.

The core statement is:

• 図書館に寄るつもり = the intention to stop by the library

Adding です makes it a standard polite sentence:

• 図書館に寄るつもりです

This is common in everyday polite Japanese.

A casual version might be:

• 仕事が終わったら、図書館に寄るつもり。

Grammatically, yes: 〜たら can mean if as well as when.

But in this sentence, the natural interpretation is when or after, because finishing work is a normal expected event, not a doubtful condition.

So in context:

• grammatical possibility: if work ends
• natural meaning: when work ends / after work is over

Yes, that is a very natural translation.

Even though the Japanese literally says something closer to:

• When work has ended, I intend to stop by the library

in natural English, After work, I plan to stop by the library is an excellent translation.

That is often the best way to translate Japanese smoothly rather than word-for-word.