Is a pollen grain a single cell?

Anther- The terminal pollen sac of a stamen, inside which pollen grains harboring male gametes form in the flower of an angiosperm.

Haploid- The condition of having only one kind of a given type of chromosome.

Within the pollen sacs of the anther, numerous microspore mother cells (1) undergo meiosis to produce four haploid microspores (2-3). Within each microspore, a mitotic division results in the formation of two {nuclei;} a thickening of the outer layer also occurs. The result of this process is four pollen grains .

https://en.wikipedia.org/wiki/Pollen

Pollen grains are single cells in most flowering plants, but several cells in other plants.

Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell. In flowering plants the vegetative tube cell produces the pollen tube, and the generative cell divides to form the two sperm cells.

https://en.wikipedia.org/wiki/Pollen