zài gōngyuán sànbù de shíhou, wǒmen yīnggāi zhùyì zìjǐ de jiànkāng.

When we take a walk in the park, we should pay attention to our health.

Breakdown of zài gōngyuán sànbù de shíhou, wǒmen yīnggāi zhùyì zìjǐ de jiànkāng.

• 的de: possessive particle
• 我们wǒmen: we
• 应该yīnggāi: should

Questions & Answers about zài gōngyuán sànbù de shíhou, wǒmen yīnggāi zhùyì zìjǐ de jiànkāng.

What exactly is the function of 在 (zài) at the beginning of 在公园散步的时候? Could we leave it out?

Here 在 introduces a location (the park) for the action 散步 (to take a walk).

• 在公园散步的时候 literally: when (we are) walking in the park
• Structure: 在 + place + verb + 的时候

Can we omit 在?

• 在公园散步的时候 – natural, standard.
• 公园散步的时候 – sounds a bit off; native speakers will usually keep 在 before a place word for “at/in (a place)” here.

So in this sentence, 在 is needed to clearly mark 公园 as the place where the walking happens.

Why do we need 的 in 散步的时候? Why not just 散步时?

散步的时候 and 散步时 are both grammatically correct, but they differ in style and tone:

• 散步的时候

  • Very common in spoken and informal Chinese.
  • Literally: the time of walking → when (we are) walking.

• 散步时

  • Shorter and feels a bit more formal or written.
  • Often used in written language, headlines, or more compact style.

So:

• 在公园散步的时候，我们应该注意自己的健康。 – perfectly natural conversational style.
• 在公园散步时，我们应该注意自己的健康。 – slightly more concise/formal.

You cannot say 散步的时 (that’s incorrect); it must be 的时候 or shortened to 时.