I-L:

I.C.: "imum coeli" or "lowest heaven"; the fourth house cusp. The most intimate and personal point in the chart: one’s innermost feelings, roots, and internal sense of self.

Inconjunct: originally applied to both the semisextile (30°) and the quincunx (150°) by Ptolemy and other Greeks; now refers to the quincunx only.

Inharmonious(ly): an aspect or sign detracting from or blocking the energy of the planet in question.

Inner (Planet): Mercury, Venus, or Mars.

Intercepted: said of a sign falling within a house and not on a house cusp. In that condition, that sign’s ruler doesn’t rule any house.

Interstellar: referring to the space between the stars. The expanding solar wind from our Sun eventually runs into the solar winds of other stars at a boundary marking the end of the Sun’s influence (and separating our solar system from interstellar space) known as the "heliopause." Thought to be about 10 billion miles - three time Pluto’s distance - from the Sun, the heliopause may soon be reached by the Voyagers 1 and 2 launched back in 1977. The Oort cloud may also mark the physical end of our solar system and the beginning of interstellar space.

Kelvin: the absolute scale of temperature, which begins at the point at which there is no atomic or molecular motion known as "absolute zero." This is 459° below 0 on the Fahrenheit scale, and is the definition of 0° on the Kelvin scale. See "plasma" for an explanation of temperature, absolute zero, and the four states of matter.

Kuiper Belt: a disk-shaped region of many small icy bodies extending from just beyond Neptune’s orbit to about three times further out from the Sun. It’s estimated to contain more than 35,000 objects greater than 60 miles in diameter (several hundred times the number of similar-sized objects in the asteroid belt), and as many as 100 million comets 12 or so miles across. Pluto is thought to be a Kuiper belt object and not a true planet because of its small size and the extreme inclination and ellipticity of its orbit.

Lights, The: the Sun and the Moon.

Light Year: the distance light travels in one year; at the speed of 186,282 miles/second, this amounts to a distance of 5.88 trillion miles. Notice that a light year is a unit of distance, not of time. The nearest star is 4.22 light years away, and our own galaxy, the Milky Way, is a spiral of 200 billion stars that is 10,000 light years thick at its central bulge and 100,000 light years in diameter. The nearest galaxy to us, the Andromeda galaxy, is 2.3 million light years away, and the entire Universe is thought to be about 27.4 billion light years across.

Line of Apsides: the major (or long) axis of an elliptical orbit; an apsis is that point in the orbit of a planet or moon nearest to (lower apsis) or farthest from (higher apsis) the center of attraction.