Which fungal infection affects the nails?

Onychomycosis is the specific term used for a fungal infection that affects the nails. This condition can lead to changes in nail color, thickness, and texture, and often results in nails that may appear discolored or brittle. The organism responsible for onychomycosis is typically a dermatophyte, but it may also be caused by yeasts or non-dermatophyte molds.

Paronychia, while relating to a nail infection, primarily refers to inflammation of the tissue surrounding the nail rather than the nail itself. Tinea pedis, commonly known as athlete's foot, is a fungal infection that affects the skin on the feet and does not directly involve the nails. Blue fingernails can occur due to various health issues, including inadequate oxygenation of the blood, but it does not indicate a fungal infection.

Thus, onychomycosis is the most accurate choice for describing a fungal infection that specifically targets the nails.