M is an n-dim orientable closed manifold.The simplicial volume is the infimum of the ${l^1}$norm of the elements $\sum {{a_i}{\sigma _i}} $ which represent the fundamental class.Where ${a_i}$ are real coefficients.My question is since ${\sigma _i}$ is a continuous map from the n-dim simlex to M.What does ${a_i}{\sigma _i}$ mean?It's a continuous map from the n-dim simlex to M?I don't know how to explain it.

For an $n$-dimensional orientable closed manifold $M$, the simplicial volume is the infimum of the $l^1$-norm of the elements $\sum a_i \sigma_i$ ($a_i \in \mathbb{R}$) which represent the fundamental class. My question is: since $\sigma_i$ is a continuous map from the $n$-dimensional simplex to $M$, what does $a_i \sigma_i$ mean? Is it the same kind of map? I don't know how to make sense of this expression.