The Component Definition subnode under Reduced Flexible Components is used for selecting the domains that form a reduced component. By default, a number of Component Definition nodes are automatically generated when a selection is made in the parent node. Each Component Definition node then contains a selection of domains that form a contiguous object, based on an analysis of the geometry.

You can modify the initial automatic selections, and add or remove Component Definition nodes as needed. To make manual selections possible, you must set Component Definition to User defined in the parent node.

The Component Definition node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).

Select the Number of eigenmodes to be used when building this reduced component. The default is From parent. Select User defined to enter another value.

Physics tab with Reduced Flexible Components node selected in the model tree: