Answer:
More particles per unit volume
Step-by-step explanation:
Concentration means the amount of solute in a solution. Now, the amount of solute also means the number of particles of solute present in a solution.
Hence, when we use the term "high concentration", we imply that the amount of solute present or the number of particles present in a solution is high.
Thus, at high concentration, there are more solute particles than solvent particles in a solution.