• In popular language grass means a short, green, ground covering or lawn, usually, but not necessarily comprised of a "true grass" or grasses, called turf. See also pasture, grass (material) .
• In botany, grass refers to plants of the family Poaceae. These are the true grasses.
• Plants that are not true grasses include:
  • China grass or remie or rhea (Boehmeria nivea), a nettle grown for bast fibres, in the family Urticaceae
  • Ditch grass or Wigeon grass (Ruppia maritima) in the family Ruppiaceae
  • Fish grass (Cabomba caroliniana)
  • Goosegrass (Galium aparine)
  • Mondo grass or lily turf (Ophiopogon japonicus), an Asian ornamental ground cover
  • Nutgrass, a common lawn pest (Cyperus rotundus) in the family Cyperaceae
  • Pepper grasses (Lipidium spp.) in the family Brassicaceae
  • Sawgrass, abundant in sub-tropical marshlands (Cladium spp.) in the family Cyperaceae
  • Scurvy-grass (Cochlearia species) in the family Brassicaceae
  • Scurvy-grass Sorrel (Oxalis enneaphylla) in the family Oxalidaceae
  • Seagrasses, including Eel grass (Zostera spp.)
  • "Sleeping grass" (Mimosa pudica) a legume (family Fabaceae) and lawn pest
  • Xyridaceae, known as the yellow-eyed grass family
• Grass is slang for marijuana or for a criminal who informs on his accomplices.
• GRASS for "GRAphics Symbiosis System" is a computer programming language
• GRASS GIS (Geographic Resources Analysis Support System) is an Open source geographic information system.