zhège nǚrén zài mǎi shícái.

This woman is buying ingredients.

Breakdown of zhège nǚrén zài mǎi shícái.

• 在zài: progressive marker
• 买mǎi: to buy
• 这个zhège: this
• 食材shícái: food ingredients

Questions & Answers about zhège nǚrén zài mǎi shícái.

Why is 在 used before 买 here?

In this sentence, 在 + verb shows that an action is in progress, similar to English is buying.

So:

• 买 = buy
• 在买 = is buying / is in the middle of buying

That is why 这个女人在买食材 means This woman is buying ingredients, not just This woman buys ingredients.

A few comparisons:

• 这个女人买食材。 = This woman buys ingredients / This woman buys ingredients in general
• 这个女人在买食材。 = This woman is buying ingredients right now

Why doesn’t the sentence use 是 for is buying?

Because 是 is not used like English to be before most verbs.

In English, we say:

• She is buying

But in Mandarin, you usually do not say 她是买...

Instead, you use:

• the verb directly: 她买食材
• or 在 + verb for an ongoing action: 她在买食材

So 是 is mainly used to link nouns or noun phrases, as in:

• 她是老师。 = She is a teacher.

But with action verbs like 买, 吃, 看, 写, you usually do not put 是 before them.