When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity respond to

Paracrine signalling

Explanation:

Paracrine signalling is a type of cell to cell signaling in which a signal is transferred from sender cell to a recipient cell.

In paracrine signalling the cell release a signal (paracrine factors) that affect the behaviour of nearby cells. These chemical signals can diffuse across the short distance and these signals are secreted in extracellular environment by cell. For a recipient cell to receive the paracrine signal it must have specific receptors or in other words it must be competent. The cells which are close to each other use the paracrine signalling for communication.

Example; During developmental process like spinal cord development paracrine signalling is used by cell to tell the other cells to adopt specific cellular identity.