The concern is whether they will approve the proposal.
In this sentence 'whether they will approve the proposal' is an example of -

• The concern is whether they will approve the proposal.
- In this sentence 'whether they will approve the proposal' is an example of - Noun clause.
- Linking verb এরপরে complement হিসাবে এটি noun clause হবে।

• A noun clause is a group of words that band together and act like a noun.
- Nouns clauses are used when a single word isn't enough.
- They're always dependent clauses.

• একটি বাক্যের চারটি স্থানে Noun clause বসতে পারে -
1. Subject হিসাবে,
যেমন: Whether they will come remains a mystery.

2. Transitive verb এর object হিসেবে,
যেমন: I believe what you have said.

3. Linking verb এরপরে complement হিসাবে,
যেমন: The reason is why they are angry.

4. Preposition এর object হিসেবে,
যেমন: He is not interested in what we have to offer.

More Examples:
1) The challenge is whether we can meet the deadline.
- এখানে, "whether we can meet the deadline" হচ্ছে - Noun clause.

2) The problem is whether you are willing to take the risk.
- এখানে, "whether you are willing to take the risk" হচ্ছে - Noun clause.

3) The discussion is whether we should invest in the new venture.
- এখানে, "whether we should invest in the new venture" হচ্ছে - Noun clause.

4) The decision depends on whether they agree with the terms.
- এখানে, "whether they agree with the terms" হচ্ছে - Noun clause.