• The words 'several' and 'whoever' act as examples of - Indefinite pronoun.

• Indefinite pronoun:
এই pronoun টি অনির্দিষ্ট কোন ব্যক্তি বা বস্তুকে বুঝায়। এগুলো সাধারণত বাক্যের শুরুতে বসে।
যেমন - Anyone, Someone, Some, All, Any, A few ইত্যাদি।

• Pronoun ৯ প্রকার। যথা:

1. Personal pronoun (He, They).
2. Possessive pronoun (Mine, Ours).
3. Reflexive pronoun and Emphatic pronoun (Myself, Ourselves).
4. Demonstrative pronoun (This, Those).
5. Indefinite pronoun (None, Several, Anyone, Someone, Several, All, Whoever).
6. Relative pronoun (Which, Where).
7. Interrogative pronoun (Who, Whom).
8. Distributive pronoun (Each, Either).
9. Reciprocal pronoun (Each other, One another).

তবে, Possessive pronoun কে অনেকক্ষেত্রে Personal pronoun এর অন্তর্ভূক্ত ধরা হয়। সে হিসেবে Pronoun ৮ প্রকার।

Example Sentence:
1. Anyone can participate in the competition.
2. Someone left their umbrella in the hallway.
3. Several are interested in the job position.
4. All is forgiven.
5. Whoever wants to join the team is welcome.

Here, Anyone, Someone, Several, All, Whoever - Indefinite Pronoun.

Source:
1. Applied English Grammar and Composition by P C Das.
2. Advanced Learner’s Grammar & Composition by Chowdhury & Hossain.