doryoku ga hitsuyou desu.

to be

Breakdown of doryoku ga hitsuyou desu.

• が: subject particle
• 必要ひつよう: necessary
• 努力どりょく: effort

Questions & Answers about doryoku ga hitsuyou desu.

Why is the particle が used in 努力が必要です?

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.

Could I say 努力は必要です instead?

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.

What kind of word is 必要? Is it a verb?