The n represents haploid condition. It means the cell possesses a half number of chromosomes. For example, in human 23 chromosomes shows n condition. The 2n represents diploid condition. It means the cell possesses two sets of chromosomes. For example, in human 46 chromosomes shows 2n condition. The n + n represents dikaryotic condition. It means the cell possesses 2 nuclei along with 2 sets of the chromosome. When these 2 nuclei unite, the cell shows 2n condition.