saikin wa suimin no shitsu o ageru apuri toka hon toka ga takusan dete imasu.

Recently, many apps and books that improve sleep quality have come out.

Breakdown of saikin wa suimin no shitsu o ageru apuri toka hon toka ga takusan dete imasu.

• は: topic particle
• 本ほん: book
• を: direct object particle
• が: subject particle

Questions & Answers about saikin wa suimin no shitsu o ageru apuri toka hon toka ga takusan dete imasu.

Why does the sentence start with 最近は instead of just 最近? What does は do here?

最近は uses は to mark 最近 as the topic of the sentence.

• 最近 = recently / these days
• 最近は = As for recently / These days, …

So the sentence is really:

最近は, (そういうものが) たくさん出ています。
As for recently, (those kinds of things) are coming out a lot.

Without は, just 最近, it would feel more like a plain adverb, “recently”:

• 最近たくさん出ています。
  → “Recently, a lot [of them] have come out.”

Both are grammatical. 最近は adds the feeling of “talking about the general situation these days,” setting up a broader, ongoing trend, not just “recently, at some point.”

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In 睡眠の質, what is the function of の?

の here is a possessive/attributive marker, similar to English "’s" or "of".

• 睡眠（すいみん） = sleep
• 質（しつ） = quality
• 睡眠の質 = the quality of (one’s) sleep / sleep quality

So X の Y often maps to “Y of X” or “X’s Y” in English.

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Why is を used before 上げる in 睡眠の質を上げる?