What condition is defined as a fungal infection affecting the nails?

The condition defined as a fungal infection affecting the nails is referred to as fingernail fungus, or onychomycosis. This infection typically occurs when fungi enter through small cracks in the nail or skin surrounding the nail, leading to symptoms like discoloration, thickening of the nail, and loosening or crumbling of the nail.

Fingernail fungus is specifically caused by dermatophytes, yeasts, or non-dermatophyte molds, which thrive in warm, moist environments, making nails an ideal target. The terminology clearly indicates that it is a fungal issue distinct from other types of nail concerns.

Other answer choices, such as bacterial infection, ingrown nail, and external nail trauma, pertain to different nail conditions and causes. Bacterial infections involve harmful bacteria rather than fungi, ingrown nails occur when the nail grows into the surrounding skin leading to pain and possible infection but not due to fungus, and external nail trauma refers to physical damage to the nail rather than an infection. Therefore, the specificity of the term "fingernail fungus" directly aligns with the definition of a fungal infection affecting the nails.