Final answer:
Hyponatremia refers to a lower-than-normal concentration of sodium in the blood, which can lead to cell swelling and serious health issues.
Step-by-step explanation:
Abnormally low blood sodium concentration is known specifically as hyponatremia. This condition is usually associated with excess water accumulation in the body, which dilutes the sodium content. Hyponatremia can result from a variety of conditions, such as excessive sweating, vomiting, diarrhea, the use of diuretics, conditions like diabetes, and metabolic acidosis. The imbalance of sodium affects cellular function because it results in increased entry of water into cells by osmosis, leading to cell swelling and potentially severe health complications, including brain damage or death.