Today's word is URBS, which is a feminine third-declension noun, genitive: urbis. It is an i-stem noun, so the genitive plural is usually spelled urbium.
Latin meaning and usage: The basic meaning of urbs is a walled town or city.
Latin word formation: From urbs we get the adjective urbanus (and its opposite: inurbanus) and the abstract noun urbanitas. There are also the compounds formed with sub- such as suburbanus, suburbium, etc.
English cognates and derivatives: We get the English words "urban" and "suburb" (and "suburban") from this root, as well as the word "urbane," with all its positive connotations.
Here are some examples of today's word in Latin sayings and proverbs; for more examples, see the page at the Scala Sapientiae, which also contains notes on some of the proverbs cited below:
anno Urbis conditae = a.U.c.
Regnant qualibet urbe lupi.
Alme sol, possis nihil urbe roma visere maius.
Urbs hominem erudit ipsa.
Concordia civium murus urbium.
Urbes constituit aetas, hora dissolvit; momento fit cinis, diu silva.
Leonis catulus in urbe non est alendus.
Qui fuit hic asinus, non fiet in urbe caballus.
Melior est qui dominatur animo suo expugnatore urbium.
Divina natura dedit agros, ars humana aedificavit urbes.
Non oportet in urbe nutrire leonem.
Otium et reges prius et beatas perdidit urbes.
Solitudo placet Musis, urbs est inimica poetis.