Erect means build or upright. If you erect a house, you build it. If you stand erect, you hold your body as tall as possible.
A mathematical model is a description of a system using mathematical concepts and language.The process of building a mathematical model is termed mathematical modeling.Mathematical models are used in the natural sciences (such as physics, biology, earth science, meteorology) and engineering disciplines (e.g. computer science, artificial intelligence). mathematical model is a description of a system using mathematical concepts and language.
Modelling is an additive process. This means a soft material is worked by the artist to build up a shape or form (rather than scraping or material away as in carving). Also unlike carving, soft materials such as clay and wax can be changed and reworked. Modelling a maquette can also often be the first step in the creation of a finished sculpture.