Focusing on the grammaticalization processes, this paper examines the evolution of "ought (to)" and "should" in the English language from historical to present-day usage. It begins by addressing key terminological concepts such as grammar, modality, and mood. The study categorizes these constructions, noting the complexities in their classification. It then analyzes their semantic and morphosyntactic changes over time, ultimately linking these developments to the principles of grammaticalization proposed by Lehmann and Hopper.
