Identifying the adjectives in the sentence:

The adjectives in the sentence are:
- "red" (describing the color of the shirt)
Explanation:
- Adjectives are words that describe or modify nouns or pronouns.
- In the given sentence, the adjective is "red" which describes the color of the shirt.
- The word "was" is not an adjective, it is a past tense form of the verb "to be".
- The word "shirt" is a noun, not an adjective.
Summary:
- The adjective in the sentence is "red", which describes the color of the shirt.

Adjectives in the Sentence:
The adjective in the given sentence is 'red'.

Explanation:
In the sentence "He was wearing a red shirt," the adjective 'red' describes the noun 'shirt'. Adjectives are words that modify or describe nouns or pronouns, providing more information about their qualities or attributes. In this case, 'red' describes the color of the shirt the person is wearing.

Definition of an Adjective:
An adjective is a word that describes or modifies a noun or pronoun. It provides additional information about the noun or pronoun by answering questions such as 'what kind', 'which one', 'how many', or 'how much'. Adjectives can also indicate size, shape, color, or other qualities.

Types of Adjectives:
There are several types of adjectives, including:

1. Descriptive Adjectives: These adjectives provide information about the characteristics or qualities of a noun. In the given sentence, 'red' is a descriptive adjective as it describes the color of the shirt.

2. Quantitative Adjectives: These adjectives indicate the quantity or amount of the noun. Examples include 'many', 'few', 'some', 'several', etc.

3. Demonstrative Adjectives: These adjectives point out or indicate specific nouns. Examples include 'this', 'that', 'these', and 'those'.

4. Comparative and Superlative Adjectives: These adjectives compare two or more nouns. Comparative adjectives are used to compare two things, while superlative adjectives are used to compare three or more things.

5. Possessive Adjectives: These adjectives indicate ownership or possession. Examples include 'my', 'your', 'his', 'her', 'our', and 'their'.

6. Interrogative Adjectives: These adjectives are used to ask questions about the noun. Examples include 'which', 'what', and 'whose'.

7. Indefinite Adjectives: These adjectives refer to non-specific or unidentified nouns. Examples include 'some', 'any', 'several', 'few', 'many', 'all', 'each', 'most', 'no', 'every', etc.

In the given sentence, 'red' is a descriptive adjective that describes the color of the shirt. It provides additional information about the noun 'shirt' by specifying its color.