The word **脑瘤 (nǎoliú)** is formed through straightforward semantic compounding in Chinese, where two meaningful characters combine to create a new, specific term. The first character, **脑 (nǎo)**, means "brain," and the second character, **瘤 (liú)**, means "tumor" or "swelling." When joined, they follow a modifier-noun structure common in Chinese, where "brain" modifies "tumor," directly and logically yielding the meaning "brain tumor." This construction exemplifies how Chinese frequently creates precise medical or technical vocabulary by combining root characters that describe the location and the condition.