doryoku ga hituyou desu.

が marks 努力 as the thing that is needed.

A very natural way to think about the pattern is:

• X が 必要です = X is necessary / X is needed

So in this sentence, 努力 is the thing being identified as necessary.

This is different from English, where we often say We need effort or Effort is necessary. Japanese commonly uses the pattern X が 必要 rather than a verb like need in this kind of sentence.

Yes, you can, but the nuance changes.

• 努力が必要です: simply states that effort is necessary.
• 努力は必要です: puts effort in contrast or marks it as the topic, as if saying As for effort, it is necessary or At least effort is necessary.

So:

• が is more neutral for introducing what is necessary.
• は often adds topic or contrast.

If you are just learning the basic pattern, 努力が必要です is the safest version.

No, 必要 is not a verb.

It is usually treated as a na-adjective or noun-like word meaning necessary or need.

That is why it can appear with です:

• 必要です = is necessary

And it can also modify nouns with な:

• 必要なもの = necessary things
• 必要な努力 = necessary effort

So in 努力が必要です, 必要 is the predicate, and です gives it a polite ending.

です makes the sentence polite.

Compare:

• 努力が必要です = polite
• 努力が必要だ = plain
• 努力が必要 = very plain / informal, depending on context

Since 必要 is not a verb, です is not functioning like do/does/is in English exactly. It is a polite copula-like ending that makes the sentence sound complete and polite.

Not necessarily. Japanese often leaves out subjects when they are obvious or unimportant.

努力が必要です can stand on its own and simply mean:

• Effort is necessary
• You need effort
• It requires effort

The exact English translation depends on context.

For example:

• talking about success: Success requires effort
• giving advice to a student: You need effort
• making a general statement: Effort is necessary

Japanese often does not spell out who needs it unless that information matters.

Both 必要 and 要る can relate to needing, but they are used differently.

• 努力が必要です = Effort is necessary
• 努力が要ります = Effort is needed / It takes effort

These are close in meaning, but 必要です sounds a bit more formal, objective, and explanatory.
要る is a normal verb and can sound a little more direct or conversational depending on context.

For a learner, X が 必要です is a very useful and common pattern to know.

努力 usually means effort, hard work, or striving. It often has a slightly stronger nuance than the English word effort by itself.

It suggests:

• making a serious attempt
• working hard toward a goal
• sustained effort, not just a small try

So 努力が必要です can feel like:

• Hard work is necessary
• Real effort is needed

depending on context.

It can absolutely be used by itself, but in real conversation it often appears with more context.

For example:

• 成功するには、努力が必要です。
  To succeed, effort is necessary.

• 日本語の勉強には努力が必要です。
  Learning Japanese requires effort.

By itself, 努力が必要です is grammatically complete, but listeners will usually understand the fuller meaning from the situation.

A simple pronunciation guide is:

• 努力 = どりょく = do-ryo-ku
• が = ga
• 必要 = ひつよう = hi-tsu-yo-o
• です = desu (though in natural speech the u is often very light)

So the whole sentence is:

do-ryo-ku ga hi-tsu-yō desu

A few useful notes:

• りょ in どりょく is one combined sound, not ri-yo
• ひつよう has a long よう sound
• です often sounds closer to des in everyday speech

Yes.

Here are common versions:

• 努力が必要です = polite
• 努力が必要だ = plain
• 努力が必要 = casual, often used in speech or notes

If you are speaking to a teacher, stranger, or in a formal setting, use 努力が必要です.
If you are talking casually with friends or writing informally, 努力が必要だ is also common.

Japanese does not use articles like English does.

So 努力 can mean:

• effort
• the effort
• an effort
• efforts

depending on context.

That is normal in Japanese. The listener understands the intended meaning from the situation, not from an article.

So 努力が必要です is not missing anything. It is a complete and natural Japanese sentence.