Joint

1 in geology, fractures in rock that may occur as parallel sets or, more commonly, in an irregular and less systematic manner. Where a set of joints can be identified, it can usually be related to tectonic (that is to do with deformation of the Earth) stresses and the geometry of the rock body. There are several types of joint: unloading joints, which are caused by the release of stress on rocks at depth as overlying rocks are removed by erosion; cooling joints, which occur in igneous bodies; and joints that are related to regional deformation (on a wide scale).

2 In biology, the point at which bones and the surrounding tissues meet. They may be fixed joints (as in the cranium), slightly movable (e.g., joints in the spine) or freely movable (e.g., knee, arm). The movable joint types also differ -- ball and socket (hip) or hinge (elbow).

Taken from Dictionary of Science

Ultracentrifuge

a special centrifuge machine that generates high centrifugal forces as it is capable of spinning at speeds up to 50,000 revolutions per minute. The ultracentrifuge is most commonly used during the separation of the various ORGANELLES within cells. The larger and more dense organelles will form a deposit in the centrifuge tube more readily than the smaller, less dense ones. The nucleus is the largest organelle of any normal cell and will be deposited at the bottom of a centrifuge tube when the ultracentrifuge spins at a force of 600g for 10 minutes, whereas the smaller MITOCHONDRION needs a higher speed of 15,000 g for 5 minutes to be deposited.

Taken from Dictionary of Science

Y-Axis

the "vertical" axis when constructing and plotting a graph

Taken from Dictionary of Science

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The vertical axis of a two-dimensional plot in Cartesian coordinates. Physicists and astronomers sometimes call this axis the ordinate, although that term is more commonly used to refer to coordinates along the -axis.

Taken from Wolfram MathWorld