ね

1. 1Seeks the listener's agreement about something both can observe or know.Ex. 1
2. 2Expresses the speaker's impression or feeling and invites the listener to share it.Ex. 2
3. 3Checks, confirms or recalls information with the listener, like 'right?'.

Used constantly in everyday conversation, in both casual speech (面白かったね) and polite speech (いいですね). It treats the content as common ground that the listener shares, which makes it the everyday way to make small talk or react together. Unlike よ, which presents something as new to the listener, ね invites agreement or confirmation.

• よN5「よ」 tells the listener something they don't know or emphasizes your own claim, and it can also follow commands or invitations to urge the listener on; 「ね」, by contrast, assumes the listener already knows or agrees. When giving someone new information, you must use 「よ」, not 「ね」.
• なN5Prohibitive 「な」 follows a verb's dictionary form to mean "don't…" and sounds harsh, while 「ね」 gently seeks empathy or confirmation. 「行くな」 forbids the listener from going, but 「行くね」 carries no prohibition at all, so the two are not interchangeable.
• だろうN5「だろう」 resembles 「ね」 only when said with rising intonation to confirm, and even then it implies inference and sounds casual; it also has a conjectural "probably…" meaning. It attaches to the plain form (nouns and な-adjectives take the stem) and is replaced by 「でしょう」 with superiors, whereas 「ね」 can also follow polite forms.
• でしょうN5「でしょう」 also expresses conjecture (as in weather forecasts), which 「ね」 lacks, but both can be said with rising intonation to confirm with the listener, and there they partly overlap. 「でしょう」 attaches to the plain form (nouns and な-adjectives without 「だ」), while 「ね」 can also follow polite forms.
• じゃないかN4「じゃないか」 can also express exclamation or confirmation, but it asserts more strongly, often implies surprise, and has a casual, masculine tone; after the volitional form it makes an energetic call to action, more forceful than 「行こうね」. It can also express reproach, which 「ね」 cannot, and it follows nouns without 「だ」.

「ね」 assumes the listener already knows or agrees and seeks empathy or confirmation, so new information or your own assertions call for 「よ」 instead; prohibitive 「な」 after a verb's dictionary form is harsh and never interchangeable with 「ね」. 「だろう」 and 「でしょう」 can partly replace 「ね」 when said with rising intonation to confirm, but they also express conjecture (and 「だろう」 sounds casual), while 「じゃないか」 asserts more strongly, often conveys surprise, and can express reproach, none of which 「ね」 does.