यह अच्छी पहल है।

Because पहल is a feminine noun in Hindi, and the adjective अच्छा changes to agree with it.

The adjective अच्छा has these common forms:

• अच्छा — masculine singular
• अच्छी — feminine
• अच्छे — masculine plural / some other masculine contexts

So:

• अच्छा विचार = a good idea (विचार is masculine)
• अच्छी पहल = a good initiative (पहल is feminine)

That is why the sentence uses अच्छी.

पहल is a noun meaning initiative, step, or first move depending on context.

In this sentence, it means something like:

• initiative
• positive step
• good move

It is also important grammatically that पहल is feminine, which is why the adjective becomes अच्छी.

Here यह most naturally means this.

So the structure is:

• यह = this
• अच्छी पहल = good initiative
• है = is

In some contexts, यह can also work like it / this / he / she depending on what is being referred to, because Hindi often uses demonstratives where English uses personal pronouns. But in this sentence, this is the most natural reading.

है is the present-tense form of to be, meaning is.

Hindi often puts the verb at or near the end of the sentence, so:

• यह अच्छी पहल है। literally: This good initiative is. natural English: This is a good initiative.

That final है is completely normal Hindi word order.

Hindi usually does not require an indefinite article like English a/an.

So:

• यह अच्छी पहल है। = This is a good initiative.

If you want, you can also say:

• यह एक अच्छी पहल है।

Here एक literally means one, but it can also function like a/an.
Both versions are correct. Without एक, the sentence still sounds perfectly natural.

Hindi and English organize sentences differently.

In this sentence, Hindi follows a pattern like:

• यह = this
• अच्छी पहल = good initiative
• है = is

So Hindi says:

• This good initiative is

but English says:

• This is a good initiative

Two key things to notice:

1. Adjectives come before nouns in Hindi, just as in English:

   • अच्छी पहल = good initiative

2. The verb है often comes at the end:

   • यह अच्छी पहल है।

The dictionary form is usually अच्छा, meaning good.

It changes form depending on the gender and number of the noun:

• अच्छा लड़का = good boy
• अच्छी लड़की = good girl
• अच्छे लड़के = good boys

So in your sentence:

• base adjective: अच्छा
• used form: अच्छी
• reason: it agrees with feminine पहल

Because the sentence is talking about one thing: यह = this.

• है is singular: is
• हैं is plural or respectful: are

So:

• यह अच्छी पहल है। = This is a good initiative.
• ये अच्छी पहलें हैं। = These are good initiatives.

Since यह is singular here, है is correct.

A simple pronunciation guide is:

yah / yeh ach-chhee pahal hai

A few notes:

• यह is often pronounced more like yeh in everyday speech, even though it is written यह
• अच्छी has a clear -chchh- sound: ach-chhee
• पहल is roughly pahal
• है sounds like hai

So the whole sentence is approximately:

yeh ach-chhee pahal hai

This is a very common point of confusion.

In standard written Hindi:

• यह = this
• ये = these

But in everyday speech, यह is often pronounced like ये / yeh, so learners may hear very little difference.

So for your sentence, the standard written form is:

• यह अच्छी पहल है।

Even if a speaker says it aloud more like ये अच्छी पहल है, the intended meaning may still be singular this is a good initiative.

So remember:

• spelling: यह
• common pronunciation: often closer to yeh

Yes. पहल has a broader sense than just one rigid English word.

Depending on context, it can be understood as:

• initiative
• step
• move
• effort
• measure

So यह अच्छी पहल है। could be translated naturally in different ways, such as:

• This is a good initiative.
• This is a positive step.
• This is a good move.

The exact English choice depends on the situation.