Which of the following terms refers to a skin infection?

Cellulitis is indeed the term that refers specifically to a skin infection. It is characterized by an acute, spreading infection of the skin and subcutaneous tissues, typically caused by bacteria such as Streptococcus or Staphylococcus. This condition often presents with symptoms like redness, swelling, warmth, and pain in the affected area, and it can sometimes lead to systemic symptoms such as fever.

In contrast, dermatitis generally refers to inflammation of the skin due to various causes, which can include allergies, irritants, or other inflammatory conditions, but is not necessarily infectious in nature. Psoriasis is a chronic autoimmune condition that causes rapid skin cell proliferation, leading to thick, silvery scales, and while it affects the skin, it is not an infection. Folliculitis is an infection or inflammation of hair follicles, often presenting with small boils or pustules, but it is more localized than cellulitis and can involve other factors like friction or blockage of hair follicles.

Thus, when categorizing skin conditions based on their nature and cause, cellulitis stands out as the primary term that denotes a skin infection.