spine

The bony column that lends its shape to most of the word's other meanings. Latin spīna meant both "thorn" and "backbone", so the word reached English already holding the needlelike spine alongside this one. Melville, in Moby-Dick (1851), saw an animal's vertebrae as "a strung necklace of dwarfed skulls." Backbone is the everyday equivalent. Spinal column and vertebral column are the terms anatomy and medicine prefer.

Courage pictured as an upright back, the figurative cousin of the backbone. In this use the word usually takes no article. Sydney I. Landau's Dictionaries: The Art and Craft of Lexicography (2001) praises "dictionary publishers with spine" who can resist pressure. Have spine, show spine and lack the spine to do something are the natural frames. Backbone works the same way.

Here the word stays closest to its Latin root, the "thorn" in the backbone sense's story. Botany uses it narrowly: a spine grows from a leaf or part of a leaf. A thorn is a modified stem, and a prickle is an outgrowth of the surface. Zoologists and mycologists use it more loosely. Darwin, in Descent of Man (1871), describes "stiff, straight spines, like those of a comb" on a male's tail.

A shape that travels across fields. Peter Hyatt's Masters of Light (2007) calls a lift core "the structural spine of the building," with two towers cantilevered from it. Sergei Matveev, writing in 2007, uses "spine" for a precise object in topology, a polyhedron inside a manifold. Unlike the "core" sense, this one keeps the physical likeness: something long and central that other parts hang from.

The most abstract stretch of the backbone image. In Gay Community News (1979), Michael Bronski writes that two themes "form the spine of a sly, knowing, and ultimately uncompassionate novel." Form the spine of is the usual frame. Unlike the backbone-shaped structure, nothing here needs to look like a spine; what matters is that the whole depends on it.

Neuroscience shortens dendritic spine to spine once the dendrite is clear from context. The short form then builds compounds of its own: spine heads are the globular tips where the synapses form. Like the full term, it is a countable noun, so writers speak of spines on a dendrite. Each spine typically receives input from a single axon.

Geologists use this word when lava is too stiff to flow. Instead of spreading down the slope, the lava is pushed upward out of the vent as a single coherent mass and stands as a tall column. The name comes from shape rather than function: the sharp, upright form is closer to a thorn-like spine than to a backbone.

The core of a trunk is dead, dense xylem that no longer carries sap but still bears the tree's weight, much as the backbone bears a body. Heartwood is the name most readers know. When spine is used of timber, it means this inner wood, as opposed to the living sapwood around it, and has nothing to do with thorns on the bark.