Abstract <p>Molybdenum disulfide (MoS₂), a prototypical two-dimensional transition metal dichalcogenide (TMD), has attracted substantial interest for its tunable properties and broad technological potential. This review presents a comprehensive comparison between monolayer and bulk MoS₂, highlighting key differences in their structural, optical, electrical, mechanical, and bio-interactive properties. The transition from bulk to monolayer induces a transformation from an indirect to a direct bandgap, significantly enhancing photoluminescence, charge mobility, and surface sensitivity features critical for next-generation electronic, optoelectronic, and biosensing devices. We also explore state-of-the-art synthesis strategies, including top-down and bottom-up approaches, that enable the scalable production of high-quality monolayer MoS₂. By synthesizing insights from recent theoretical and experimental advances, this article elucidates why monolayer MoS₂ consistently outperforms its bulk counterpart in functional applications ranging from strain sensors and photodetectors to non-invasive biosensors for prenatal diagnostics. The review not only maps the current landscape but also outlines future directions, positioning monolayer MoS₂ as a cornerstone material for advanced technologies.</p>