Final answer:
Pneumonia is an acute infectious disease that affects the lower respiratory tract, causing inflammation and fluid-filled alveoli. It is characterized by symptoms such as shortness of breath, coughing, chest pain, and fever. Streptococcus pneumoniae is a common pathogen associated with pneumonia.
Step-by-step explanation:
Pneumonia is an acute infectious disease caused by a bacterium or virus that affects the lower respiratory tract and causes lung inflammation and fluid-filled alveoli. It is characterized by symptoms such as shortness of breath, coughing, chest pain, and fever. Pneumonia can be caused by various pathogens, with Streptococcus pneumoniae being one of the most common.