Mental is a concept mapping app for the iPad.

Concept maps organize knowledge in the form of a graph of concepts. Concepts are represented as a noun phrase enclosed in a rectangular box, and are connected to other concept boxes by arrows labeled with a verb or conjunction. These arrows and labels define the relationships between the connected concepts. Concept boxes may have relationships to and from several other concept boxes, creating a graph of concepts, or concept map.

Users create concept maps as autosaved documents. In a concept map, they are able to create and remove concept boxes, edit the enclosed text, and move the boxes at will around a zoomable and pannable canvas.

They can create relationships to connect the concepts, a relationship being represented by at least three graphical objects:
⁃ an editable label signifying the relationship;
⁃ one or more edges connecting the 'subject' concepts to the label;
⁃ one or more edges connecting the label to the 'object' concepts.
Users are able to move the labels at will, the edge connections being preserved. They may remove relationships as a whole, or individual edges while preserving the relationship.

Other features:
⁃ export to pdf and sharing;
⁃ map style chooser (font, color scheme).