Translation guide
In Japanese, the concept of viscosity is expressed through several terms that distinguish between the physical property of fluids and the subjective sense of thickness or stickiness. The most common technical term is 粘度 (nendo), while 粘性 (nensei) is used in physics and engineering. For everyday descriptions of thick or sticky liquids, 粘り気 (nebari-ke) and とろみ (toromi) are more natural.
Referring to the measurable resistance of a fluid to flow, as in physics or engineering contexts.
The standard technical term for viscosity, used in scientific and industrial contexts. Often paired with 高い/低い (high/low).
This liquid has a high viscosity.
温度が上がると粘度が下がる。
Viscosity decreases as temperature rises.
Used in physics and rheology, often in compound terms like 粘性率 (coefficient of viscosity). Slightly more formal/academic than 粘度.
水の粘性は温度によって変化する。
The viscosity of water changes with temperature.
Describing a liquid that is thick, gooey, or sticky in a non-technical sense, like syrup or glue.
Refers to stickiness or glutinous quality. Commonly used for foods (natto, mochi) or adhesives.
このソースは粘り気が強すぎる。
This sauce is too thick and sticky.
納豆の粘り気が好きだ。
I like the sticky texture of natto.
Describes a pleasantly thick, syrupy consistency, often used for sauces, soups, or cosmetics. Implies a smooth, flowing thickness rather than stickiness.
A colloquial noun form of 粘っこい (sticky), emphasizing an unpleasant or excessive stickiness.
このご飯は粘っこさが足りない。
This rice isn't sticky enough.
Metaphorical use, such as 'viscosity of bureaucracy' or 'social viscosity'.
Literally 'rigidity', sometimes used metaphorically for organizational inertia. Not a direct translation of viscosity, but conveys similar idea in context.
組織の硬直性が問題だ。
The viscosity (rigidity) of the organization is a problem.
粘度 is the most common word for viscosity in everyday technical contexts (e.g., motor oil, cooking). 粘性 is more academic and appears in physics. 粘り気 refers to the sensory quality of stickiness, not a measurable property.
粘度 is only for fluids. For sticky solids or semi-solids (like tape or glue stick), use 粘着力 (adhesion) or 粘り気.
Thicken the soup (give it viscosity).
この化粧水はとろみがある。
This lotion has a viscous texture.