How is と used in these sentences?

Question

I have some sentences that involve the usage of と that I still don't understand:

1. This is from another user's post

私はあなたがいつも忙しいと分かっています。

2. My previous question

いつもと変えてたまに外で食事しよう。

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At the very basic level, this post pretty much sums up what I understand about と. I added a few more usages based on what I learnt so far.

• Quotation or defining particle

e.g. [X]は日本語でなんと言いますか？How do you say [X] in Japanese?

e.g. 日本語は難しいと思います。(I) think Japanese is difficult.

e.g. 彼は明日来ると言った｡ He said that he will come tomorrow.

• Conditional particle

e.g. 彼は暇だといつもゲームをしているの。If he is free, he always plays games.

• List of things

e.g. ナイフとフォークでステーキを食べた。(I) ate steak with a knife and fork.

• With/Partner of interaction/Accompaniment

e.g. 友達と映画に行った｡(I) went to watch a movie with my friend.

e.g. 父と似ている。(I) resemble my father.

• Objects of similarity/difference

e.g. 私の意見は彼の意見と異なる。My opinion is different from everyone.

e.g. いつもと同じ電車です。(It) is the same train as usual.

• Sound/Onomatopoeia

e.g. 星がきらきらと輝いている｡The stars are twinkling.

I understand there are many more uses of と that I did not include in the list and that I may not be aware of.

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I have trouble connecting both of the sentences above into one of the listed categories.

But if I had to guess, と under sentence 1 is used as a Quotation or defining particle? Such as the second example 日本語は難しいと思います。

And for sentence 2, I see it used like いつもと同じ電車です under Objects of similarity/difference.

But I'm confused here because 変える is not a "similarity" but a "change from usual". However, I might have a misconception that と is not just used for objects of similarity or differences in this particular case.

Can someone explain how と is used in each of the sentences above? I would appreciate similar examples like ones provided above to help me understand how と is used in these cases, and I'm really thankful to anyone who can help clear up my confusion with this particle.

Answer 1

As for your first sentence, you're right that the と is a quotative particle.
It's often used with a verb that introduces one's utterance or thought, e.g. 言う, 思う, 感じる, 知る, 分かる, 話す, etc.

A few examples:

嫌だと言う
危ないと感じる
やめようと思った
痛いと顔をしかめる _{(「言って」「思って」 etc. are occasionally left out)}
これが最後と別れを惜しむ
(examples above taken from 明鏡国語辞典)
正しいという結論に達する
(from デジタル大辞泉)

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As for your second sentence, you're right again that the と indicates 「比較・類別の際に照合される相手」(明鏡国語辞典) , 「比較の基準」(デジタル大辞泉), or "Object of Similarity/Difference" in your list.
The と is often used with a verb or adjective that expresses difference, change, similarity, identity (sameness), or comparison, e.g. 同じ, 違う, 異なる, 似る, 比べる, etc. and it functions like "(same) as..." "(different/differentiate) from..." "(similar) to..." "(compare) with...". In your example, ～と変える is used to mean "change from...". _{(～と変える can also mean "change into~~" (≂～に変える) depending on context, and the と here indicates 動作の結果. By the way, ～と[代]{か}える/[替]{か}える can mean "exchange for~~/replace with~~", where the と indicates 動作の対象.)}

A few examples:

あなたと同じ考えだ
以前とは条件が異なる
父[子]は子[父]と似ている
(examples taken from 明鏡国語辞典)
君のとは比べものにならない
昔と違う
(from デジタル大辞泉)

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By the way, the example 父と似ている。(I) resemble my father is categorized in With/Partner of interaction/Accompaniment in your list, but I think it should fall under Objects of similarity/difference.

Answer 2

1. 私はあなたがいつも忙しいと分かっています。

Question A:

と under sentence 1 is used as a Quotation or defining particle? Such as the second example 日本語は難しいと思います。

Yes, it is. I'll show you the reason.
日本語は難しいと思います could be rewritten as:
(a)「日本語は難しい」と思います。
Sentence 1 could be rewritten as:
(b)「あなたがいつも忙しい」と私は分かっています。
と in (a) and (b) has the same function as quotation or defining particle.

2. いつもと変えてたまに外で食事しよう。

Question B:

と is not just used for objects of similarity or differences in this particular case.

と in 2 is not used for objects of similarity or differences.
Why do you have the idea that と in 2 is like that in 私の意見は彼の意見と異なる or that in いつもと同じ電車です?
There is no such suggestions in the answers here.
I think いつもと(変える) in 2 means "(change) from a usual manner/custom".
Anyway some words are omitted in 2, so the omission might make you confused.
The full text of 2 might be like:
- いつもの習慣{しゅうかん}/やり方｛かた｝ と変えてたまに外で食事しよう。
- いつも家｛いえ｝で食｛た｝べるという習慣｛しゅうかん｝ と変えてたまに外で食事しよう。