A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals. Plants with characteristics that make them hazardous, aesthetically unappealing, difficult to control in managed environments, or otherwise unwanted in farm land, orchards, gardens, lawns, parks, recreational spaces, residential and industrial areas, may all be considered weeds. The concept of weeds is particularly significant in agriculture, where the presence of weeds in fields used to grow crops may cause major losses in yields. Invasive species, plants introduced to an environment where their presence negatively impacts the overall functioning and biodiversity of the ecosystem, may also sometimes be considered weeds.

Ohalo II is an archaeological site in Northern Israel, near Kinneret, on the southwest shore of the Sea of Galilee. It is one of the best preserved hunter-gatherer archaeological sites of the Last Glacial Maximum, radiocarbon dated to around 23,000 BP (calibrated). It is at the junction of the Upper Paleolithic and the Epipaleolithic, and has been attributed to both periods. The site is significant for two findings which are the world's oldest: the earliest brushwood dwellings and evidence for the earliest small-scale plant cultivation, some 11,000 years before the onset of agriculture. The numerous fruit and cereal grain remains preserved in anaerobic conditions under silt and water are also exceedingly rare due to their general quick decomposition.