The distribution of particles across space from high concentration to low concentration

This question is asking to state what is being defined. The term defined in the question is called DIFFUSION

Explanation:

Diffusion is the movement of particles/fluids from a region where they are highly concentrated to the region where they are less in concentration across a space. Diffusion is a form of passive transport i.e does not require energy input to occur. This is because the movement occurs down a concentration gradient.

A concentration gradient i.e difference in concentration occurs when there is an uneven amount/concentration of particles in two regions. Hence, movement occurs naturally to the direction where the particles are less concentrated from where they are more concentrated.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]