PRIMARY USES: 1) Destination (“to”) Use に to mark where someone or something goes. Common verbs: いきます, きます, かえります. 2) Existence / location (“at / in”) Use に with あります／います to mark where something exists. This is not the location of an action; it is the location of being. 3) Specific time (“at / on”) Use に to mark a specific time point (clock times, days, dates). It marks a moment when an action happens. OTHER COMMON USES: 4) Recipient (“to”) Use に to mark the recipient of giving, lending, teaching, calling, or meeting (depending on the verb). It marks who receives something, or who the action is directed toward. 5) Purpose (“for the purpose of”) Use に with movement verbs to express purpose, often with a verb stem or a noun. Examples include going somewhere to do something. LITMUS TESTS: 1) If the noun is a destination and the verb is “go/come/return” → use に. 2) If the verb is あります／います and you mean “is located” → use に. 3) If the noun is a specific time (like 7:00, Monday, January 3rd) → use に. 4) If the action is directed toward a person as a recipient → use に. 5) If you mean “go somewhere in order to do X” → use に. COMMON CONFUSIONS (に vs other particles): に vs で: - に = where something exists or the destination of movement. - で = where an action happens (the setting of an activity). If the verb is あります／います → usually に. If the verb is an action verb like study/eat/play → usually で. に vs へ: - に = destination (endpoint) and is the more common choice. - へ = direction (“toward”), focusing on movement rather than arrival. If you mean arriving at a destination → に. If you want to emphasize direction or heading → へ. に vs を: - を marks the direct object. - に marks destination/time/recipient. If you can ask “what did you do?” → を. If you can ask “to where / to whom / at what time?” → に. TIME NOTE: に is often omitted with vague time words like 今日, あした, きのう, まいにち, まいしゅう, etc. に is most natural with specific time points.