Connectors link elements together, and are typically represented as lines on diagrams showing how the elements relate to each other. Making a comparison to natural languages, if the elements are nouns the Connectors are verbs that describe how the nouns relate to each other.
The connector types are defined by the modeling languages or profiles they belong to. For example, Associations and Generalizations are part of the grammar of UML; Sequence Flows and Message Flows are part of the grammar of BPMN; and Allocates and Item Flows are part of the grammar of SysML. Each connector type has a notation that helps modelers recognize the connector and understand its purpose; the types also inform tools such as the Code Templates Framework how to generate resulting models, schemas or programming code.
Connectors can be viewed in a wide range of windows, such as the Relationships Window, the Hierarchy Window, the Relationship Matrix, the 'Element' tab of the Browser window and the 'Properties' dialog for an element.