An ester is a compound formed by the reaction between a carboxylic acid and an alcohol. The general formula for an ester is \( RCOOR' \), where \( R \) and \( R' \) are alkyl or aryl groups.
- \( \text{CH}_3\text{COOH} \) is acetic acid (a carboxylic acid),
- \( \text{CH}_3\text{COOCH}_3 \) is methyl acetate (an ester),
- \( \text{CH}_3\text{OH} \) is methanol (an alcohol),
- \( \text{C}_6\text{H}_6 \) is benzene (an aromatic hydrocarbon).
Thus, \( \text{CH}_3\text{COOCH}_3 \) is an ester.