1. (Science: botany) a coloured, usually green, expansion growing from the side of a stem or rootstock, in which the sap for the use of the plant is elaborated under the influence of light; one of the parts of a plant which collectively constitute its foliage.
Such leaves usually consist of a blade, or lamina, supported upon a leafstalk or petiole, which, continued through the blade as the midrib, gives off woody ribs and veins that support the cellular texture. The petiole has usually some sort of an appendage on each side of its base, which is called the stipule. The green parenchyma of the leaf is covered with a thin epiderm pierced with closable microscopic openings, known as stomata.
2. (Science: botany) a special organ of vegetation in the form of a lateral outgrowth from the stem, whether appearing as a part of the foliage, or as a cotyledon, a scale, a bract, a spine, or a tendril.
3. Something which is like a leaf in being wide and thin and having a flat surface, or in being attached to a larger body by one edge or end; as: a part of a book or folded sheet containing two pages upon its opposite sides. A side, division, or part, that slides or is hinged, as of window shutters, folding doors, etc. The movable side of a table. A very thin plate; as, gold leaf. A portion of fat lying in a separate fold or layer. One of the teeth of a pinion, especially when small.
(Science: zoology) leaf beetle, any beetle which feeds upon leaves; especially, any species of the family Chrysomelidae, as the potato beetle and helmet beetle. Leaf bridge, a draw-bridge having a platform or leaf which swings vertically on hinges.
(Science: botany) leaf bud, a sawfiy. To turn over a new leaf, to make a radical change for the better in one's way of living or doing. They were both determined to turn over a new leaf. (Richardson) The main organ of photosynthesis and transpiration in higher plants.Produce leaves, of plants.The photosynthetic region of plants, where different species exhibit different types of leaves to suit their function. This diversity of plant leaves has been brought about by natural selection attempt.