$\mathcal{E}$ represents all the possible *experiences*, and $\mathcal{C}$ represents all the *concepts* (an illustration is presented in Fig \[fig:example\_color\]).

A knowledge-like function $f \in \mathcal F$ is a function from the experience set $\mathcal{E}$ to the concept set $\mathcal{C}$.

Each knowledge-like function represents represents the knowledge of one individual. Let $e$ be in $\mathcal{E}$, when there is a $ c \in \mathcal{C}$ such as $f(e) = c$ and $c \neq 0$, we say that the knowledge-like function *conceptualizes* $e$. We assume that individuals conceptualize all experiences they go through. Elements that are not conceptualized (i.e. not experienced) by individuals are sent to the zero of the set $\mathcal{C}$ by their knowledge-like function.

#### Example. The knowledge-like function associated to colors.

Let $\mathcal{E}$ be $[0, 1000] \subset \mathbb{R}$ representing the set of wavelengths in nanometers. We remind that $[380, 750]$ is the set of the visible spectrum. An individual associates each element of $\mathcal{E}$ to a color as shown in Figure \[fig:example\_color\]. The set of concepts $\mathcal{C}$ contains the name of the color and $0$. In this case $\mathcal{E}$ is a continuous space and $\mathcal{C}$ is a discrete space.

A knowledge-like function associates a color to each wavelength, or 0 if 