**Definition:**  

Cefalexin, also known as Cephalexin, is a first-generation cephalosporin antibiotic. It is a semi-synthetic derivative designed to effectively treat bacterial infections by targeting the bacterial cell wall.  

**Function:**  

Cefalexin works by inhibiting the synthesis of the bacterial cell wall, leading to cell lysis and death. It is effective against a wide range of Gram-positive and some Gram-negative bacteria, making it a versatile choice for combating infections.  

**Applications:**  

Cefalexin is commonly used to treat respiratory tract infections, skin and soft tissue infections, urinary tract infections, and otitis media. It is available in oral formulations, including capsules, tablets, and suspensions, making it convenient for outpatient use and mild to moderate infections.