rotation
Pluralrotations (some meanings)
- 1The act or motion of spinning or turning about a center or an axis, as a wheel or planet does.
The rotation of the planet on its axis takes about twenty-four hours.
Friction gradually slowed the rotation of the spinning top.
Similarspinning, turning, revolution, spin
Note
Latin rotatiō lies behind the word, though English speakers can also read it as rotate plus -ion, the suffix that turns a verb into the act of doing it. In this sense it is chiefly uncountable: the earth's rotation about its axis, the rotation of water going down a drain. When you start counting separate turns, you have moved to a single complete turn.
- 2A single complete turn around a center point or an axis.
Each rotation of the Earth marks one full day.
The motor's shaft makes thousands of rotations per minute.
Similarrevolution, turn, spin, cycle
- 3A regular cycle in which people take turns at a task or items are used in order to even out wear; also a duty roster.
Crop rotation keeps the soil healthy by changing what is planted each season.
The team posted the new rotation showing who covers each weekend.
Similarrota, roster, cycle, alternation, schedule
Note
Taking turns is the heart of it, and the word applies to fields, staff and trainees alike. Crop rotation changes what a field grows so its soil is not exhausted. The phrase in rotation means each person in order. A medical resident does a two-week rotation in pediatrics, so a rotation can also be a single stint within the cycle.
- 4The repeated playing of a song or advertisement on a radio station or television channel over a period of time.
The station added the band's latest track to its daily rotation.
Once a hit drops out of rotation, listeners rarely hear it again.
Similarairplay
Note
Broadcasting has its own version of turn-taking: a station's playlist comes round again and again. The set phrase is heavy rotation, meaning frequent play, as when a new single enjoys heavy rotation on MTV. A track can also be added to rotation, kept in rotation, or dropped out of it.
- 5In baseball, the set of starting pitchers a team cycles through over successive games.
The manager slotted the veteran into the back of the rotation.
A five-man rotation gives each starter four days of rest.
Note
Baseball borrows the turn-taking sense: starters take the mound in a fixed order, typically four or five of them, each resting several days between starts. A pitcher is said to be in or out of the rotation, and a newcomer slotted into the back of it starts after the established arms.
- 6A transformation that turns a figure around a fixed point while preserving all distances between points.
A rotation about the origin maps each point to a new position the same distance away.
Combining a rotation with a reflection produces another rigid motion of the plane.
Note
The mathematician's version keeps only two requirements: no distance may change, and at least one point must stay put. Spin is not written into the definition, yet the result behaves like spin. The map sending (x, y) to (−y, x) is a quarter turn about the origin, and in the plane every other point moves through the same angle around the fixed center.
- 7The movement of investment money between sectors of the economy or styles of investing, based on expected shifts in the market cycle.
Analysts noted a rotation from growth stocks into value names as rates rose.
A defensive rotation into utilities often signals worry about a slowdown.
Similarshift
Note
Finance distinguishes two kinds. Sector rotation moves money between parts of the economy expected to do well in the coming phase. Style rotation moves it between ways of investing, such as from growth toward value. The word usually takes from or out of, then into: a rotation out of one corner of the market and into another.
- 8The point during the takeoff roll when the pilot raises the aircraft's nose wheel off the ground.
The first officer called out the speed for rotation as the jet gathered pace.
A premature rotation can cause the tail to strike the runway.
Note
In aviation the word names a moment rather than a continuing motion. The aircraft is still rolling down the runway when the pilot, on reaching rotation speed, applies back pressure and the nose wheel lifts. That sets up the initial climb attitude, and timing matters: rotate too early and the tail can strike the runway.
Practice
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Origin
Borrowed from Latin rotatiō; by surface analysis, it is rotate plus the suffix -ion.