The is used before a noun to show that you are talking about a specific person or thing that is already known or has been mentioned. It points to something particular, not just any example.
From Old English *se, seo, þæt* (different gender forms), which gradually merged into a single form. Over time it lost its gender and case endings and became the single, all‑purpose article we use today.
English has only one little word, 'the', to do the work that many languages spread across several forms. It’s the most common word in English, quietly gluing almost every sentence together.
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