と

The particle と is one of the most common particles in Japanese. Its usage depends on the context:

• Exhaustive 'And': When connecting nouns (Noun A と Noun B), it implies the list is complete. Unlike や, which implies 'and others,' と means 'only these.' Note that と can connect nouns, pronouns, and noun phrases. To connect adjectives, you must use the て form.
• Accompaniment ('With'): It marks the person or animal you perform an action with. It implies a mutual relationship, and is explicitly required for reciprocal verbs that need a mutual participant (e.g., 結婚する（けっこんする - to marry）, 喧嘩する（けんかする - to fight）, 離婚する（りこんする - to divorce）), where English speakers might mistakenly use the direct object marker を.
• Quotation Marker: It follows a statement (direct or indirect) before verbs like 言う（いう - to say） or 思う（おもう - to think）. In casual spoken Japanese, と is overwhelmingly replaced by って (e.g., 「行く」って言った instead of 「行く」と言った). It is also used to quote sounds or specific actions (e.g., ドカンと鳴る - to make a 'bang' sound). It is also essential in the noun-modifier pattern 〜という (called/named, e.g., 「ポチ」という犬 - a dog called Pochi). Furthermore, when used after a volitional verb (ようとする), it means 'trying to do' or 'about to do' something.
• Natural Condition ('When/If'): When following a verb in its plain/short form (including the negative ない form), it indicates that one action naturally or automatically leads to another. Because this pattern expresses an inevitable or natural result, it usually translates better to 'whenever' or 'when' rather than a hypothetical 'if' (which is better handled by たら or ば). Important: The second clause cannot contain a command, request, or personal will (e.g., てください, ましょう, or たい). See と (conditional).
• Discovery ('When'): Used to describe a realization or immediate sequence where the second clause is in the past tense, meaning 'When I did X, I discovered/noticed Y' (e.g., 窓を開けると、海が見えた - When I opened the window, I saw the ocean).
• Adverbial Use: It is often used with onomatopoeia or mimetic words to describe how an action is performed (e.g., ゆっくりと - slowly, ぼーっと - absentmindedly).
• Comparison: It is used to compare things, often appearing in phrases like と同じ（とおなじ - same as）. It is also essential in the core comparison pattern 'A と B と、どちらが...' (Which is more, A or B?).
• Result/Change/Decision: Used with なる（to become） to indicate a final result or state (e.g., 〜となる). Its transitive counterpart, とする, means to treat something as, to assume, or to decide on (e.g., こととする or 〜とする).

Note: While と can follow verbs to show conditions or immediate succession, it cannot be used to connect verbs like 'and' does in English. A common beginner mistake is trying to say 食べる（たべる）と飲む（のむ） to mean 'eat and drink'. To connect actions in a sequence, use the て form, or to list representative actions, use たり.