Functional Definition: 

Solubility is the ability of a solute to dissolve in a solvent. How soluble something is depends on its state as a solid, liquid or gas  and the state of its solvent. Usually solvents are liquids such as water or ethanol. Factors like polarity,  pressure, temperature, and pH determine how soluble the solute is. Remember from beginning chemistry that solubility is measured in mg/ml and refers to how likely a solute is to dissolve in a pure solvent. It’s unlikely that you’ll be asked what the solubility of something is but keep in mind that knowing the solubility of  your experimental components can make your life easier and allow you to make informed decisions about what solvents to use.