Elongation
The angular distance that a planet forms to the Sun as viewed from the Earth, which is measured in degrees, minutes and seconds of arc. The elongation of the outer planets can range from 0 to 180 degrees which means that they can form any kind of aspect to the Sun.
The situation is different with the inner planets: Mercury can at most be situated 28 degrees from the Sun and can be found either in the same sign of the zodiac as the Sun or in one of the two signs bracketing it. This means that apart from a conjunction the only other aspect Mercury can make to the Sun is the rather rarely used Semi-Octile (22.5 degrees). Being two signs away from the Sun for Mercury is not possible - even at the end or beginning of a sign.
In addition to the semi-octile that Mercury can form, Venus can also form a semi-sextile (30 degrees) or a semi-square (45 degrees) to the Sun, in addition to the rarely used decile (36 degrees - which is also known as the semi-quintile - and the novile (40 degrees).