tributary=a river or stream flowing into a larger river or lake.支流（delta三角洲；estuary河口；gulf海湾）
Mississippi river has many tributaries on which many people depend for fishing and transportation.
Mississippi river has many tributaries on which many people base fishing and transportation.
可以用现在完成时表示“和现在情况相反的事”，这个时候不需要“过去时”出现就可以用过去完成时，如：
Some scientists suggest that the moon is actually older than we had originally thought.
I had thought this should be an easy task but it is not.
protoplanet= a large body of matter in orbit around the sun or a star and thought to be developing into a planet，胚胎行星（注意proto是表示“初始、先驱”的前缀，比如prototype，预案）
Astronomers believe the moon was formed by a protoplanet crashing into the earth, flinging off（pv，vt摆脱）a rocky piece which became the moon when our solar system was in its chaotic days.
molten=（especially of materials with a high melting point，such as metal and glass）liquefied by heat.熔化的
This large amount of molten iron is the raw material（注意raw material 是原材料，source material 是原始资料） for steel.
magma= hot fluid or semifluid material below or within the earth’s crust from which lava and other igneous rock is formed on cooling.岩浆，不可数
The energy from the impact of a protoplanet on the earth created a molten lunar magma ocean that eventually became the moon’s surface.
In comes new technology.（一种煞有介事的倒装）
Atom probe tomography（APT），原子针尖断层影像仪，其实主要记住tomography是断层呈像技术（a technique for displaying a representation of a cross section(横截面）through a human body or other solid object using X-ray or ultrasound），而且atom probe tomography是最精尖的，能实现纳米（nanometer）级别呈像的技术；比atom probe tomography水平低一些的是computerized tomography（CT），也就是骨折时候人们常说的“拍个片儿”中的“片儿”，这个片儿其实是不同角度的X光（X-ray）呈像的合成；最低水平的就是X-ray呈像技术。（另外需要注意，tomography是断层呈像技术，而topography是“地形”的意思）
Pencil sharpener卷笔刀，可数
Pencil sharpener plays an important role in primary school students’ life.
hourglass=an invertible（可颠倒的）device with two connected glass bulbs（bulb除了可以作电灯泡讲，也可以作球状物讲）containing sand that takes an hour to pass from the upper to the lower bulb.沙漏，可数
She has an hourglass figure.（她腰细）
Spectrometer 分光计，used for measuring spectra（spectrum光谱的复数）
Rendition 演绎，通过自己的理解去表演某角色或音乐，可数
People think Joe’s rendition of ‘forests in Norway’ is as good as its original singer Wu Bai.
lo and behold= used to express surprise or wonder
Lo and beh old, virtually without air resistance on the surface of the moon, a feather and a hammer at the same height can fall to the ground at the same time.
我一直以为只有一个阿波罗（apollo）号登上过月球，没想过5个阿波罗号登上过5次月球。
reach 作vt 是抵达、达成的意思，作vi 和for 连用是伸手够的意思
If you’ve still got pumpkins to carve, don’t reach for your kitchen knife because you might hurt yourself.
Wobbly=tending to move unsteadily from side to side摇晃的
This table is wobbly and I gather it’s gonna break up soon.
workbench 工作台，可数；a kitchen island 厨房中岛，也就是厨房中间的大桌子，四面都不靠墙，可以准备饭菜也可以做饭，桌子下面的抽屉还能储藏餐具。
serrated=having or denoting a jagged edge锯齿状的
knives with a serrated edge are more suitable to cut bread.
razor blade剃须刀刀片，可数
Jack-o’-lantern= a lantern made from a hollowed-out pumpkin万圣节南瓜灯
patriot 爱国者，可数；patriotic爱国的（以后说爱国的人直接说patriots，不用说patriotic people了）
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