1 at rest :(1)resting or reposing especially in sleep or death (2)quiescent, motionless(3): free of anxieties
2 work out :to bring about by labor and exertion
b : to solve (as a problem) by a process of reasoning or calculation
c : to devise, arrange, or achieve by resolving difficulties
d : develop
Eg.by putting our heads together, we were able to work out the problem.
3 elliptical : shaped like a flattened circle(椭圆）
: using few words and therefore hard to understand
Eg. The moon follows an elliptical path around the Earth.
a writer with an elliptical style
4 spiral: winding or circling around a central point and usually getting closer to or farther away from it : shaped or moving like a spiral.
Eg.a spiral staircase takes visitors up into the Statue of Liberty.
5 stub: noun a short part left after a larger part has been broken off or used up
: a part of a ticket that is kept by the person who uses the ticket
: a piece of paper that is attached to a check and has information (such as the amount and the date) printed on it
Eg.Hold onto your ticket stub in case you leave the theater and want to come back in again.
transitive verb: to put out (a cigarette) by pressing it down against something. to strike (one's foot or toe) against an object(脚趾踢到物体上）
Eg. Stubbed his toe on a large stone.
6 commonsense : the ability to think and behave in a reasonable way and to make good decisions
synonyms :see sense
Eg.You really should go to see a doctor if your leg hurts that much. It's just common sense!
7 ether : a liquid that burns easily, that is used to turn solid substances into liquid, and that was used in medicine in the past to prevent patients from feeling pain during operations（醚）
: the air : the sky
Eg.The balloon disappeared into the ether.
8 postulate :transitive verb:to suggest (something, such as an idea or theory) especially in order to start a discussion
Eg.Scientists have postulated the existence of water on the planet.
Noun:
: a statement that is accepted as being true and that is used as the basis of a theory, argument, etc.
Eg.a hypothesis advanced as an essential presupposition, condition, or premise of a train of reasoning.
9 in effect:in fact actually
10 cesium :铯
cesium clock铯原子钟（利用元素铯的原子振动频率量度时间的原子钟）
11 validity :the state of being legally or officially acceptable
Eg. The period of validity of the agreement has expired.
12 coordinate noun : one of a set of numbers that is used to locate a point on a map, graph, etc.(坐标）
: articles of clothing that are made to be worn together
Eg.We calculated its exact coordinates.
13 diagonal of a straight line : joining two opposite corners of a shape (such as a square or rectangle) especially by crossing the center point of the shape（对角线)
: not going straight across or up and down
Eg.The blanket is covered with diagonal stripes.
14 radius : a straight line from the center of a circle or sphere to any point on the outer edge ; also : the length of this line（半径）
: an area that goes outward in all directions from a particular place
medical : the bone in the lower part of your arm on the same side as your thumb
15 geodesic : the shortest line between two points that lies in a given surface(测底线）
16 block out :to stop light or noise from coming in
Eg. Black clouds blocked out the sun.
17 crest : something suggesting a crest especially in being an upper prominence, edge, or limit: as
a : peak; especially : the top line of a mountain or hill
b : the ridge of a roof
c : the top of a wave
Eg. the hiking party reached the crest of the mountain just as it began to thunder
18 arena : a building for sports and other forms of entertainment that has a large central area surrounded by seats
: an area of activity, interest, or competition
Eg. Congress became an arena of opposing views.
19 curvature : the amount that something is curved
medical : a condition in which your spine is curved in an abnormal way
Eg. The lenses have different curvatures.
20 stack transitive verb:: to arrange (things) in a stack : to put (things) in a usually neat pile
: to cheat at a card game by arranging (a deck of cards) in a special way
—used to describe a situation in which one person, team, etc., is given an advantage over others often in a way that is unfair
Eg. She stacked the plates in the cupboard.
