>>712Solidus (plural solidi or soliduses)
1. The line between the numerator and the denominator of a fraction.
2. A forward slash or virgule.
3. A late Roman gold coin (after 3rd Century CE); a bezant.
4. (chemistry, physics) a line, in a phase diagram, below which a given substance is a stable solid and above which solid and liquid are in equilibrium
In other words, the fourth one. Neither solid nor liquid.