kinou wa kaze o hikimashita ga, ima wa daijoubu desu.

topic particle

Breakdown of kinou wa kaze o hikimashita ga, ima wa daijoubu desu.

• です: to be
• を: direct object particle
• 昨日きのう: yesterday

Questions & Answers about kinou wa kaze o hikimashita ga, ima wa daijoubu desu.

In 昨日は, why do we add は after 昨日? Isn't 昨日 just "yesterday"?

は is the topic marker. It tells you what the sentence is talking about.

• 昨日は literally means "As for yesterday," or "Yesterday (at least / in contrast)".
• The rest of the sentence, 風邪を引きましたが、今は大丈夫です, is the comment about yesterday.

So the structure is:

• 昨日は – as for yesterday
• 風邪を引きましたが、今は大丈夫です – I caught a cold, but now I'm okay.

You could say the sentence without は:

• 昨日風邪を引きましたが、今は大丈夫です。

This is also correct, but 昨日は adds a slight feeling of "speaking specifically about yesterday (as opposed to other days)". That contrastive nuance is common with は.

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Why don't we say 昨日に here? When do you use に with time words like this?