と

1. 1Connects nouns in a list meaning 'A and B', typically presenting the named items as the whole set.Ex. 1
2. 2Marks the person one does something with or together with ('with').
3. 3Marks a condition that is regularly or naturally followed by the result in the main clause ('when/whenever').Ex. 2

Neutral and common in both speech and writing. As a listing particle, と on its own presents the named items as the set, while や gives examples from a longer list. As a conditional, と suits natural laws, habits, machine operations, and directions, where the result follows automatically. Unlike たら, it generally does not take a main clause expressing the speaker's will or requests, though set phrases such as そうなると can lead into a suggestion.

• ばN4「ば」 expresses only a condition and attaches to the conditional form (書けば). It is often interchangeable with 「と」 when stating general rules, but 「ば」 focuses on the condition itself and cannot describe past realized facts; it forms patterns like 「〜ばいい」 and 「〜ばよかった」, and when the first clause is a state, the second clause can take volitional expressions.
• たらN4「たら」 is close to 「と」 only in its conditional meaning: it attaches to the た-form and tends to emphasize individual, one-time situations. When the second clause expresses volition, requests, or invitations, it cannot be replaced with 「と」; when describing a past discovery, the two are often interchangeable.
• ならN4「なら」 is close to 「と」 only in its conditional meaning: it takes up the topic raised by the other speaker and gives a judgment or advice based on the first clause as a premise. The second clause can contain advice or volition, and the action may even precede the first clause; regular changes like 「春になると」 cannot use 「なら」.
• やN5「や」 is similar only to the listing use of 「と」: 「や」 cites just a few representative examples, implying there are others, and often pairs with 「など」, whereas 「と」 lists everything. 「や」 cannot mark the partner of a joint action or a condition, and attaches only to nouns.
• としたら / とすればN3「と」 as a condition states a rule, habit, or discovery that automatically follows once something happens; 「としたら/とすれば」 is a tentative hypothesis where the first clause is uncertain or contrary to fact, the second clause is usually a conjecture, question, or judgment, and the first clause can be in the past tense.

Compared with ば, たら, and なら, conditional と stresses an automatic or habitual result: たら suits one-time events and requests, ば focuses on the condition itself, and なら responds to a topic or assumption. Listing と on its own presents the items as the set, while や implies others, and としたら / とすれば set up a purely hypothetical supposition rather than a natural consequence.