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Old English leaf "leaf of a plant; page of a book," from Proto-Germanic *laubaz (cf. Old Saxon lof, Old Norse lauf, Old Frisian laf, Dutch loof, Old High German loub, German Laub "foliage, leaves," Gothic lauf), perhaps from PIE *leup- "to peel off, break off" (cf. Lithuanian luobas, Old Church Slavonic lubu "bark, rind"). Extended 15c. to very thin sheets of metal (especially gold). Meaning "hinged flap on the side of a table" is from 1550s.
"to turn over (the pages of a book)," 1660s, from leaf (n.). The notion of a book page also is in the phrase to turn over a (new) leaf (1570s). Related: Leafed; leaved; leafing.
An appendage growing from the stem of a plant. Leaves are extremely variable in form and function according to species. For example, the needles of pine trees, the spines of cacti, and the bright red parts of the poinsettia plant are all leaves modified for different purposes. However, most leaves are flat and green and adapted to capturing sunlight and carbon dioxide for photosynthesis. They consist of an outer tissue layer (the epidermis) through which water and gases are exchanged, a spongy inner layer of cells that contain chloroplasts, and veins that supply water and minerals and carry out food. Some leaves are simple, while others are compound, consisting of multiple leaflets. The flat part of the leaf, the blade, is often attached to the stem by a leafstalk.
1. LISP Extended Algebraic Facility.
2. "LEAF: A Language which Integrates Logic, Equations and Functions", R. Barbuti et al in Logic Programming, Functions Relations and Equations, D. DeGroot et al eds, P-H 1986, pp.201-238.
of a tree. The olive-leaf mentioned Gen. 8:11. The barren fig-tree had nothing but leaves (Matt. 21:19; Mark 11:13). The oak-leaf is mentioned Isa. 1:30; 6:13. There are numerous allusions to leaves, their flourishing, their decay, and their restoration (Lev. 26:36; Isa. 34:4; Jer. 8:13; Dan. 4:12, 14, 21; Mark 11:13; 13:28). The fresh leaf is a symbol of prosperity (Ps. 1:3; Jer. 17:8; Ezek. 47:12); the faded, of decay (Job 13:25; Isa. 1:30; 64:6; Jer. 8:13). Leaf of a door (1 Kings 6:34), the valve of a folding door. Leaf of a book (Jer. 36:23), perhaps a fold of a roll.