Explanation:

Best is an adjective in this sentence as it describes the noun friend. Adjectives are words that modify or describe nouns.

Here's a detailed breakdown of the sentence:

- Selena is the subject of the sentence. It is a proper noun that refers to a specific person.
- Is is the linking verb that connects the subject Selena to the complement best friend.
- My is a possessive adjective that shows ownership. It indicates that the best friend being referred to belongs to the speaker.
- Best is the adjective that describes the noun friend. It indicates that the speaker considers Selena to be the top or most favored among their friends.

Adjectives:

Adjectives are words that describe or modify nouns. They provide additional information about the noun they are attached to. In this case, the adjective best describes the noun friend. It shows that Selena holds a special position in the speaker's circle of friends.

Other Examples:

Here are a few more examples of sentences where best is used as an adjective:

1. Selena is my best friend.
2. This is the best movie I have ever seen.
3. The cake tasted the best among all the desserts.
4. She is the best student in her class.

In each of these examples, best is used to describe a noun and provide additional information about it. Adjectives play a crucial role in bringing more detail and specificity to sentences.

Adjective