いっしょにテニスをしませんか。
- Shall we play tennis together?

いっしょにテニスをしませんか。 meaning: Won't you play tennis with me? / Shall we play tennis together?

⚫︎ This sentence is a polite invitation. The basic sentence structure is relatively simple. ⚫︎ The sentence ends with か, which indicates a question. In this case, it's a suggestion presented as a question. ⚫︎ The subject is implied and usually refers to "we" or "you and I."

⚫︎ に (ni): This particle marks the place or the person to whom an action is directed. In this sentence, it's part of the phrase いっしょに, meaning "together with." ⚫︎ を (o): This particle marks the direct object of the verb. In this case, テニス (tennis) is the object of the verb します (do). The sentence structure can be understood as "Shall we do tennis?"

⚫︎ The verb in this sentence is します (shimasu). This is the polite form (masu-form) of the verb する (suru), which means "to do". ⚫︎ しますか (shimasu ka) is used to ask a question in a polite way. It is a more polite version of する. ⚫︎ しませんか (shimasen ka) is the negative polite form of the verb, and is often used to make suggestions or invitations in a gentle way. It’s like saying, "Why don't we do...?" or "Won't you do...?"

⚫︎ いっしょに means "together" or "with." It's a fixed expression frequently used to describe doing something with someone. ⚫︎ It is followed by the particle に.

⚫︎ The sentence utilizes a common pattern to offer an invitation or suggestion. ⚫︎ The pattern involves using the negative polite form of a verb + か. For example: 食べませんか (tabemasen ka - Won't you eat?) or 行きませんか (ikimasen ka - Won't you go?). This is a softer and more polite way of making suggestions than simply stating the action.