Learn Hardcore Chinese: zhōumò wǒ hé tā qí zìxíngchē, bù kāi chē. - On weekends she and I ride bicycles and don't drive.

By itself, 周末 is a time word that relies on context. It can mean a general/habitual “on weekends” or a specific upcoming/past weekend. To be explicit:

这个周末 = this weekend
上个/下个周末 = last/next weekend
For “on weekends (habitually)”: 周末 or 每个周末/周末都 (e.g., 每个周末我们都…)

Why is 周末 placed at the beginning? Can I say 我周末… or 在周末…?

Chinese typically puts time expressions before the subject: 周末，我… or 周末我…. 我周末… is also common. 在周末 is grammatical but feels more formal/less colloquial; everyday speech usually drops 在. You can also say 周末的时候，我… for “during the weekend.”

Does 我和她 mean “she and I” or “I with her”? Should I use 跟 or 和?

我和她 can be read as a combined subject (“she and I”) and also conveys “I with her.” 和 and 跟 are both fine here; 跟 is a bit more colloquial. To make togetherness explicit, add 一起: 我跟她一起骑自行车. Note: in imperatives, 跟 is preferred (e.g., 跟我来), not 和.

Do I need to add 一起 to mean “together”?

Optional. 我和她骑自行车 already implies doing it together. 一起 just emphasizes it: 我和她一起骑自行车.

Why use 骑 for a bicycle but 开 for a car?

Chinese chooses the verb by how the vehicle is used:

骑: straddle and ride (e.g., 骑自行车/摩托车/电动车/马)
开: operate/drive (e.g., 开车/开卡车/开船/开飞机)
坐/乘/搭: take as a passenger (e.g., 坐车/坐地铁/坐公交; 搭 is colloquial in Taiwan)
打车/叫车: take a taxi

Is 骑车 the same as 骑自行车?

Usually yes; 骑车 is the short, everyday form and often means “ride a bicycle.” Where motorcycles/scooters are common, 骑车 can be ambiguous—say 骑自行车 to be clear. You’ll also hear 骑单车 (单车 = bicycle) in some regions.

Do I need a measure word with 自行车?

Only with numbers/quantity. The measure word is 辆:

一辆/两辆自行车
我们各骑一辆自行车 Without counting, just say 骑自行车.

Can I drop 车 and just say 不开?

No. 不开 alone usually means “not open/turn on.” To mean “don’t drive,” say 不开车. You can extend it: 开了一个小时的车, 开车去公司. If you mean “not go by car (as a passenger),” say 不坐车.

Why is the negative 不 and not 没?

不 negates habits, general truths, preferences, or planned/regular behavior: 我一般不开车. 没 negates past occurrences/completion: 昨天我没开车. Here the meaning is habitual or planned, so 不 is correct.

Does 不 change tone here?

No. 开 is first tone, so 不 stays fourth tone: bù kāi chē. Rule: 不 becomes second tone (bú) only before a fourth-tone syllable (e.g., 不对 bú duì, 不是 bú shì).

Why is there no 了 after 骑?

Because the sentence isn’t about a specific completed event; it’s a general statement/plan. For a completed past weekend, you could say: 上个周末我们骑了自行车，没有开车.

Who is the subject of 不开车? Why isn’t it repeated?

It’s still “I and she” (i.e., we). Chinese often omits repeated subjects in the second clause when it’s obvious from context. You can say 我们不开车 for emphasis, but it’s not required.

Is the comma expressing “instead of”? Are there clearer ways to show the contrast?

Yes, the pause plus 不 gives a contrastive “rather than.” You can make it explicit:

周末我们骑自行车，而不开车。
周末我们骑自行车，而不是开车。

Any pronunciation traps (e.g., 自行车 or 和)?

自行车: zì xíng chē (行 is xíng, not háng)
和 in this meaning is hé (second tone). It has other readings (huó/huò/hàn) in different words, but not here.

她 and 他 sound the same. Does it matter?

In speech both are tā. In writing, choose 她 (female) or 他 (male). In informal online writing, some people use gender-neutral TA.

How do I say “We ride bikes to the park (instead of driving)”?

Use the pattern 骑自行车去 + place:

周末我们骑自行车去公园，不开车。

Can I replace 我和她 with 我们 or 我们俩?

Yes. 我们 is fine. To emphasize “the two of us,” use 我们俩/我俩:

周末我们俩骑自行车，不开车。 Don’t add 们 to each pronoun separately (avoid “我和她们” unless you literally mean “I and they”).