Litera, a letter; literature, literary, letters, obliterate.
Locus, a place; location, dislocate.
Longus, long; elongate, longitude.
Loquor (locūt-us), I speak; loquacious, eloquent, elocution.
Ludo (lus-um), I play; ludicrous, allusion.
Lumen (lumin-is), light; illuminate, luminous.
Luna, the moon; Luna, sublunary, lunacy.
Luo, I wash; ablution, dilute.
Lux (luc-is), light; lucid, pellucid.
Magister, a master; magistrate, master.