What condition is characterized by a loss of language ability?

The condition characterized by a loss of language ability is aphasia. Aphasia occurs when there is damage to the areas of the brain responsible for language processing, which can affect speaking, understanding, reading, and writing. It can arise from various causes, including strokes, traumatic brain injuries, or neurological conditions.

In contrast, agnosia refers to the inability to recognize objects, people, sounds, or smells while the sensory function itself remains intact; it does not directly involve language abilities. Apraxia involves difficulty with the motor planning to perform tasks or movements, even when the person knows what they want to do and has the physical ability to do it, but again, this does not specifically pertain to language. Amnesia involves memory loss that can result from injury or psychological trauma, affecting the ability to remember past events or form new memories, but it is unrelated to language functionality.

Therefore, aphasia clearly defines the specific loss of language ability, making it the correct answer in this context.