a Particle
Together with (...), partner
友達と遊ぶ Playing (together) with friends
More formal way would be to use {共|とも}に
Two-way comparison
絵と比べる Comparing paintings
父は息子と似ている The father looks a lot like the kid.
Quotation
Nomimalises the part that comes before it, essentially turning it into a 'quote'
行かないでと言った He said "don't go".
彼が引っ越すと聞いた I heard that he will move.
資産がありませんと説明した He explained that there is no budget.
And (...)
between two nouns
リンゴとスイカ Apples and watermelons
Conditional
100% certainty. More certain than 〜たら. Therefore, it's more like 'when' than 'if'. “when X happens, Y happens”. Y is predictable or an unavoidable fact, or a natural consequence.
- “when you turn, there will be a bank”.
- “when I opened the door, snow came in”.
四月になると、桜が咲さく When it becomes april, the cherry blossoms will bloom.
先生だと、きっと年上なんじゃないですか。 If he's a teacher, it has to be the case that he is older (than us), right?
今出かけないと遅れるよ。 If you don't depart now, you will be late
学校に行かないと、友達と会えないよ If you don't go to school, then you won't meet any friends.
the だと is an often-used stylistic figure.
これだと乗り換えなし If this is the case, you don't have to transfer (trains)
愛だと運命です。 If love is what it is, it must be fate.
Less intuitive, but it shows just that two events are related: it is only when you went to the hospital that you saw Fujiwara-san. It is similar to 時に in this context.
病院に行くと{藤原|ふじわら}さんがいました。 When I went to the hospital, I saw fujiwara-san.
Must always be follow by non-past tense.
窓を~~開た~~と、牛が~~見えてきました~~。
～ようと
といい;
～ずと
Lesson 133 see Conditional forms (〜ば、〜たら、なら、と)
https://imabi.org/the-conditionals/