The term "main monosaccharide" isn't technically correct because there isn't a single, universally accepted "main" monosaccharide. However, glucose is often considered the most important monosaccharide for several reasons:

* Energy source: Glucose is the primary source of energy for most living organisms.

* Abundance: It's the most abundant monosaccharide found in nature, present in plants, fruits, and honey.

* Building block: It's a key building block for larger carbohydrates like starch, glycogen, and cellulose.

Therefore, while there isn't a "main" monosaccharide, glucose is arguably the most important and widely recognized monosaccharide.