Definitions

Periods
Principate | Wikipedia

Institutions 
Political institutions | Wikipedia

Constitution

Magistrates

Definitions
officium | Wikipedia

Magistrates | Ordinary
Consul | Wikipedia
Censor | Wikipedia
Governor | Wikipedia

Magistrates | Extraordinary 
rex | Wikipedia
dictator | Wikipedia
corrector | Wikipedia

Titles
Emperor | Wikipedia
princeps senatus | Wikipedia
legatus | Wikipedia
dux | Wikipedia
lictor | Wikipedia

Assemblies

Definitions
Roman assemblies | Wikipedia
Assemblies [kingdom] | Wikipedia

Curiate Assembly
Curiate Assembly | Wikipedia

Centuriate Assembly
Centuriate Assembly | Wikipedia

Class

Nobility
Patrician | Wikipedia
nobiles | Wikipedia

Masses
Plebeians | Wikipedia

Law

Definitions
Roman law | Wikipedia

Categories 
Æquitas | Wikipedia
mos maiorum | Wikipedia
Collegiality | Wikipedia
senatus consultum | Wikipedia

Equity

See Colleges

Custom
romanitas | Wikipedia
pietas | Wikipedia
gravitas | Wikipedia
virtus | Wikipedia
hospitium | Wikipedia
otium | Wikipedia
dignitas | Wikipedia

Power
de facto
imperium | Wikipedia
lex curiata de imperio | Wikipedia

de jure
potestas | Wikipedia
auctoritas | Wikipedia

Civil Law
Collegium
Collegium | Wikipedia

Religion | Titles
pontifex maximus

Inheritance 
fideicommissum

Sexuality
Catamite