The current literature reflects the fact that various concepts coexist and that there is not the one classical approach generally accepted. Popular as well as subjective concepts define weeds as plants growing in the wrong place, causing damage, being of no benefit and suppressing cultivated plant species.
Economical concepts reflect the view of agronomists who concentrate on the phenomena in agrosystems.
Competition between crops and weeds, which reduce yield production is central to the definition. Thereby, the damage aspect is stressed. In contrast to the previous concept, ecological definitions include habitats outside agrosystems colonised by weeds. The usual preference of weeds for anthropogenically disturbed habitats is stressed. They include cultivated fields and gardens which are artificially kept open as well as disturbed areas on road sides, recently built artificial slopes and others.