thickness
n. C / Un. the distance between the opposite sides of something. You use this to describe how wide or deep an object is, like a slice of bread or a wall.
n. the dimension of an object between two opposite surfaces; the quality of being thick. Refers to the third dimension of a solid object, distinct from length and width.
The thickness of the ice is safe for skating.
You can adjust the thickness of the slices by turning the dial on the side of the machine.
Engineers must calculate the precise thickness of the steel hull to ensure the vessel can withstand the immense pressure of deep-sea exploration.
From Middle English thikkenesse, thiknesse, from Old English þicnes (“thickness, viscosity, density, hardness; obscurity, cloud, darkness; thicket; depth, a thick body, anything thick or heavy”), from Proto-West Germanic *þikkwīnassī (“thickness”), equivalent to thick + -ness. Cognate with West Frisian tsjokkens (“thickness”), Old High German dickinessī, dikkinissi, diknissi (“thickness, density”). Eclipsed non-native Middle English crassitude (“thickness”) from Latin crassitūdō (“thickness”).
Uncountable when referring to the general quality; countable when referring to a specific layer or measurement.