Amendment & Miscellaneous
This article defines about 30 terms used throughout the Constitution, including: "agricultural income", "Anglo-Indian", "article"/"clause"/"sub-clause"/"Part"/"Schedule" (Constitution's own structural terms), "corporation tax", "existing law", "goods and services tax", "High Court", "Proclamation of Emergency" (an Article 352 Proclamation), "public notification", "Scheduled Castes"/"Scheduled Tribes" (cross-referencing Articles 341/342), "Services", "State" (with a special expanded meaning for GST-related articles, including Union Territories with a Legislature), "socially and educationally backward classes", and detailed technical definitions of "tax on the sale or purchase of goods" covering various transaction types.
This is the Constitution's master glossary - a single article collecting precise legal definitions for dozens of terms used throughout the entire document, ensuring consistent, unambiguous meaning wherever these words appear rather than each article having to separately define its own vocabulary.
Whenever you see a precise technical term like "existing law" or "corporation tax" used elsewhere in the Constitution, its exact legal meaning traces back to this one definitions article rather than being defined separately each time it's used.