This report presents MontiArc, a modeling language for the description of Component & Connector architectures. A component is a unit executing computations and/or storing data. Information flow between components is modeled via unidirectional connectors connecting typed, directed ports of the interfaces of components. Language features of the ADL MontiArc include hierarchical decomposition of components, subtyping by structural inheritance, component type definitions and reference declarations for reuse, generic component types and configurable components, syntactic sugar for connectors, and controlled implicit creation of connections and subcomponent declarations. This technical report gives an overview of the MontiArc language and is a reference for the MontiArc grammar intended to enable reuse and extension of MontiArc and MontiArc related tools. MontiArc is implemented using the DSL framework MontiCore. Available tools include an editor with syntax highlighting and code completion as well as a simulation framework with a Java code generator.