Learn Hardcore Japanese: kono apuri ha muryou de tukaeru.

は marks the topic: “As for this app…”. The sentence is making a general statement about the app’s property (that it can be used for free). The doer (people in general/you) is left implicit in Japanese.

Why is で used after 無料? Could I use に?

で marks the manner/state: “in the state of being free (of charge)” → “for free.” 無料に doesn’t mean “for free” here; 無料にする means “to make (something) free.” Since 無料 is a noun-like word, 無料で is the natural adverbial form.

Why isn’t it このアプリを無料で使える? Shouldn’t を mark the object?

With potential verbs (like 使える “can use”), the thing that would normally take を often takes が (or は if it’s the topic). So you typically say このアプリが/は無料で使える, not このアプリを無料で使える.

Can I say このアプリが無料で使える instead? What’s the nuance vs は?

Yes. が highlights or identifies the subject (“It’s this app that can be used for free,” often contrastive or new info). は presents it as the topic/background (“As for this app, it can be used for free,” neutral/explanatory).

What’s the polite version of the sentence?

このアプリは無料で使えます。 Use 〜ます for polite speech. In writing, Japanese normally doesn’t use spaces: このアプリは無料で使えます。

Does 使える mean “is allowed to use” or “is able to be used”?

Primarily “is able to be used / can be used” (ability/possibility). For permission, use expressions like 使ってもいい or 使ってよい (“may use”). Context can blur this in English, but in Japanese 使える itself isn’t the permission form.

What’s the base verb of 使える, and how is this potential form made?

Base verb: 使う (“to use”). For godan verbs, change the final sound to the “e” row and add る: 使う → 使える, 書く → 書ける, 飲む → 飲める. Polite: 使えます; negative: 使えない; polite negative: 使えません.

Could I say 使うことができる instead of 使える?

Yes: このアプリは無料で使うことができる. It’s longer and more formal. In everyday speech, 使える is more natural and concise.

Is 無料 a noun or an adjective? How do I say “a free app”?

無料 functions as a noun/na-adjective meaning “free of charge.” To modify a noun, use 無料の: 無料のアプリ (“a free app”). As an adverbial “for free,” say 無料で.

What’s the difference among 無料, タダ, and 無償?

無料: neutral/standard “free (no charge).”
タダ: casual/colloquial “free.”
無償: formal “without compensation,” used in official or business contexts.

Why is アプリ in katakana?

It’s a loanword from English “app/application.” Loanwords are written in katakana, hence アプリ. The longer form アプリケーション is also used.

Can I move 無料で around? For example, 無料でこのアプリは使える?

Yes, adverbials are flexible. このアプリは無料で使える is the default. 無料でこのアプリは使える is possible and puts emphasis on “for free.” Avoid placing 無料で after the verb: 使える無料で is unnatural.

Can I drop は in casual speech?

Yes: このアプリ、無料で使える。 Dropping は is common in casual conversation when the topic is obvious. Don’t drop で in 無料で; you need it.

How do I say the opposite (not free / can’t be used for free)?

“Can’t be used for free”: このアプリは無料で使えない。
“It’s paid/there’s a fee”: このアプリは有料だ／有料です。

What’s the difference between 無料で使える and 無料です?

無料です states “It’s free (of charge).” 無料で使える emphasizes the action/result: “(You) can use it for free.” In many app/pricing contexts both convey similar info, but 無料で使える ties it explicitly to usage.

How is this pronounced?

Kono apuri wa muryō de tsukaeru.

この (kono)
アプリ (apuri)
は (wa, pronounced “wa” when the topic particle)
無料 (muryō)
で (de)
使える (tsukaeru)

Why not これアプリ or これ instead of この?

この is a determiner used before a noun: このアプリ (“this app”). これ is a standalone pronoun (“this [thing]”). You can say これは無料で使える (“This is usable for free”), but then you’re not naming “app.”

I’ve seen 使える used like “useful” (“This app is actually useful”). Is that what it means here?

Here it’s the potential form “can be used.” In casual speech, 使える can colloquially mean “useful/handy” (e.g., このアプリ、使える！). With 無料で使える, it clearly means “usable for free,” not “useful.”