The 1957 Encyclopédie Larousse defines a cell in music as a "small rhythmic and melodic design that can be isolated, or can make up one part of a thematic context." The cell may be distinguished from the figure or motif: the 1958 Encyclopédie Fasquelle defines a cell as, "the smallest indivisible unit," unlike the motif, which may be divisible into more than one cell. "A cell can be developed, independent of its context, as a melodic fragment, it can be used as a developmental motif. It can be the source for the whole structure of the work; in that case it is called a generative cell."
A rhythmic cell is a cell without melodic connotations. It may be entirely percussive or applied to different melodic segments.