R, r 1. Abbreviation for radius. 2. The symbol for the thermal resistance of a material. 3. Abbreviation for electrical resistance.

rabbet, rebate A long channel, groove, or recess in one member to receive another as in a window or door edge, or as in tongue-and-groove lumber.

raceme In botanical terms, a flower cluster with one-flowered pedicels along the axis of inflorescence. It is a simple flower cluster with many stalked flowers about the same length coming from the same stem and usually opening in succession toward the apex.

raceme inflorescence

racemose Growing in the form of a raceme.

raceway A channel, pipe, or conduit for enclosing electrical conductors.

rachilla In botanical terms, the axis of a spikelet.

rachis In botanical terms, that which bears and is attached to flowers or leaflets of a plant. It may refer to an axis bearing close-set organs, espe cially the axis of a spike. It is also used in reference to the extension of the petiole or rib of a compound leaf from which the petiole meets the leaf blade to the tip of the leaf.

rachis radial A spine of a cactus where the spines originate from an aerole's periphery instead of its center as is the case with a central.

radial Projecting outward from a center along a radius or in a circle, as rays projecting from a point.

radial-arm saw or radial saw A saw that holds a rotating, circular saw blade above the work and has capabilities for tilting, rotating, or moving the blade.

radical Pertaining to the root.

radicle The lower part of a plant embryo. The root of a plant embryo or seedling.

radius of throw The distance from the sprinkler head to the farthest point of water application by the sprinkler.

rafter A structural support member extending from the ridge of the roof down to the eave.

raft foundation A thick, reinforced concrete slab used instead of wall or column footings or foundations to support and distribute the load of a structure to a soil with low-bearing capacity.

ragwork Thin, flat, undressed stones laid in a crude and random fashion, usually horizontally.

rail 1. An elongated item of various materials used for grasping with a hand for stability and

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