Japanese particles

は

Topic marker. Marks the topic ("as for…"). Introduces what the sentence is about. Can show contrast. Does not necessarily mark the grammatical subject. Examples: 猫はかわいい。 (As for the cat, it's cute.) 私は学生です。 (As for me, I'm a student.)

が

Subject marker. Marks the grammatical subject. Introduces new information. Used for emphasis, discoveries, and existence. Answers "who?" or "what?". Examples: 猫がいる。 (There is a cat.) 誰が来た？ (Who came?)

を

Direct object marker. Marks what receives the action. Examples: 水を飲む。 (Drink water.) 本を読む。 (Read a book.)

に

Destination / Time / Indirect object / Location / Purpose marker. Marks destination, specific time, indirect object, where something exists (with いる/ある), and purpose (usually with 行く・来る・帰る). Examples: 学校に行く。 (Go to school.) 三時に起きる。 (Wake up at 3 o'clock.) 友達に本をあげる。 (Give a book to a friend.) 部屋に猫がいる。 (There is a cat in the room.) 食べに行く。 (Go to eat.)

へ

Direction marker. Shows movement toward a direction. Less specific than に. Examples: 日本へ行く。 (Go toward Japan.) 家へ帰る。 (Go home.)

で

Location of action / Means marker. Marks where an action happens or the method/tool used. Examples: 学校で勉強する。 (Study at school.) バスで行く。 (Go by bus.) 箸で食べる。 (Eat with chopsticks.)

と

And / With / Quotation marker. Connects a complete list, means "with," and marks quotations. Examples: 犬と猫。 (Dogs and cats.) 友達と話す。 (Talk with a friend.) 「行きたくない」と言った。 (Said, "I don't want to go.")

も

Also / Too / Even marker. Means "also," "too," or "even." Examples: 私も行く。 (I'll go too.) 水も飲む。 (Drink water too.)

の

Possession / Description / Nominalizer. Shows possession, connects nouns, and can turn phrases into nouns. Examples: 私の本。 (My book.) 日本の車。 (Japanese car.)

から

From / Because marker. Indicates the starting point or gives a reason. Examples: 日本から来た。 (Came from Japan.) 疲れたから寝る。 (I'm tired, so I'll sleep.)

まで

Until / Up to marker. Marks the endpoint of time or distance. Examples: 五時まで。 (Until 5 o'clock.) 東京まで行く。 (Go as far as Tokyo.)

や

Non-exhaustive listing marker. Means "…and…, etc." Examples: 本やノート。 (Books, notebooks, etc.) 犬や猫。 (Dogs, cats, etc.)

ね

Agreement marker. Seeks confirmation or agreement, similar to "right?" or "isn't it?" Examples: それ、いいですね。 (That's nice, isn't it?) 暑いね。 (It's hot, isn't it?)

よ

Assertion marker. Adds emphasis or gives new information. Examples: 行くよ。 (I'm going!) おいしいよ。 (It's delicious.)

か

Question marker. Turns a sentence into a question. Examples: 行くか？ (Are you going?) 学生ですか。 (Are you a student?)

だけ

"Only" marker. Neutral way to say "only." Example: 水だけ飲む。 (Drink only water.)

しか

"Only" marker. Means "only," must be used with a negative verb, and implies limitation. Examples: 水しかない。 (There is only water.) 水しか飲まない。 (I drink only water.)

けど

Soft contrast marker. Means "but" and expresses casual, neutral contrast. Example: 高いけど買った。 (It's expensive, but I bought it.)

のに

Strong contrast marker. Means "even though" and often expresses disappointment or frustration. Example: 勉強したのに忘れた。 (Even though I studied, I forgot.)

でも

"But" / "Even" / "For example" marker. Means "but," can mean "even," or suggest an example ("something like"). Examples: でも行く。 (But I'll go.) コーヒーでも飲む？ (Want some coffee or something?) 子供でもできる。 (Even children can do it.)

こそ

Strong emphasis marker. Strongly emphasizes the preceding word. Examples: あなたこそ正しい。 (You are the one who's right.) 今日こそ勝つ。 (Today, I'll definitely win.)

から vs ので

Because. から is more direct and personal and is common in casual speech. Example: 寒いから帰る。 (It's cold, so I'm going home.) ので is softer and more explanatory and is common in polite speech. Example: 寒いので帰ります。 (Because it's cold, I'll go home.)