kono jishoapuri wa, reibun dake de naku hatsuon mo kikeru node benri da.

This dictionary app is convenient because you can hear the pronunciation as well as see example sentences.

Breakdown of kono jishoapuri wa, reibun dake de naku hatsuon mo kikeru node benri da.

• は: topic particle
• 便利べんり: convenient
• この: this
• だ: to be

Questions & Answers about kono jishoapuri wa, reibun dake de naku hatsuon mo kikeru node benri da.

What is the difference between この and これ, and why is it この辞書アプリ here?

この is an adjective-like word that must be followed by a noun:

• この辞書アプリ = this dictionary app (app near the speaker)

これ is a pronoun and stands alone:

• これは辞書アプリです。 = This is a dictionary app.

Because 辞書アプリ (dictionary app) is explicitly mentioned, you need この before it, not これ.
If you removed 辞書アプリ, then you would say:

• これは便利だ。 = This is convenient.

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Why is the particle は used after この辞書アプリ, and can I use が instead?

は marks the topic of the sentence – what you are talking about overall:

• この辞書アプリは…便利だ。
  As for this dictionary app, (it) is convenient.

が is mainly a subject marker, often used to introduce something new or emphasize the subject itself.

You could say:

• この辞書アプリが便利だ。

but the nuance changes slightly. この辞書アプリが便利だ sounds more like:

• This dictionary app (in particular) is the one that is convenient (perhaps compared to others).

In a neutral description about “this app,” は is the natural choice.

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How does だけでなく … も work in 例文だけでなく発音も?