在 / 正在 …呢【zài / zhèngzài … ne】

在 before a verb says the action is under way.

正在 and 呢

zhèng zài正在 pins the action to this exact moment, and ne呢 at the end makes the sentence more conversational. 在, 正在, 在…呢 and 正在…呢 all work and differ only in emphasis.

呢 on its own is enough in conversation: 他看书呢.

Negation

The negative is méi没zài在 + verb, and 正 and 呢 drop.

Verbs that refuse it

States don't progress. 是, 有, 知道, 喜欢 and 认识 take no 在.

• × 我在知道 → 我知道
• × 他在是老师 → 他是老师

No tense attached

在 marks an action in progress at whatever time the sentence is talking about, past or future.

在 or 着

在 is the action happening; zhāo着 is the state it leaves.

Two 在 in one sentence

The progressive 在 and the place 在 are both zài. When both would appear, drop the progressive one and add 呢 if you need the "right now" sense.

• × 我在家在做饭 → 我在家做饭呢