Meaning: the ordered, patterned arrangement of statuses, roles, groups and institutions that makes collective life possible — society's skeleton (Radcliffe-Brown's organic analogy: structure is to society what anatomy is to the organism — but, unlike a skeleton, it is reproduced only through continuous interaction).
Components: statuses and roles (the mesh); groups (family to state); institutions (the organised clusters); stratification (the ranking of positions — the key structural fact).
Stratification — the three classic systems:
1. Caste (birth-ascribed, endogamous, traditionally justified by ritual purity — Nepal's historical structure, legally codified in the Muluki Ain 1854 and abolished in law only across the 20th century; L. Dumont's study of it as homo hierarchicus is the theory set-text).
2. Class (economic position, at least in principle achieved — education, income, occupation; rising fast in Nepal through schooling, migration and remittance).
3. Estate/slavery (historic forms; Nepal's own versions — haliya, kamaiya, haruwa-charuwa bonded labour — legally abolished: Kamaiya (bonded labour) liberation legislation in the 2000s — but with social residues).
The law-student's summary line: social structure is what makes behaviour predictable enough for law to be possible; stratification is what makes some of that predictability unjust — and Nepal's constitutional order (equality, inclusion, federalism) is precisely a design to restructure the structure (Units 5 and 7).